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Chemoautotrophic Microbial Mats in Submarine Caves with Hydrothermal Sulphidic Springs at Cape Palinuro, Italy
Abstract
Observations were made on the distribution, morphology, and chemoautotrophic potential of microbial mats found in submarine caves of dolomitized limestone which contain hydrothermal sulphidic springs at Cape Palinuro, Italy. The distribution of microbial mats is closely associated with the flow of hydrothermal fluid from springs whose activity is intermittent and initiated during low tide. Fluid emitted from active springs in the Grotta Azzurra has a maximum temperature of 24.6°C and is enriched in dissolved sulfur species (H2S, S2O32−) and dissolved gases (CH4, CO2). However, it is depleted in NaCl and dissolved O2, in comparison with ambient seawater. This fluid is less dense and rises above the ambient seawater to form a visible thermocline and chemocline separating both layers in the submarine caves. Microbial mats were attached to rock surfaces immersed in fluid above the chemocline and were differentiated into brown and white forms. Brown mats were composed of trichomes (4.2 ± 0.1 μm and 20.3 ± 0.7 μm in diameter) resembling the calcareous rock-boring cyanobacterium Schizothrix and clusters (6 μm in diameter) of sarcina-like cells morphologically resembling methanogenic bacteria. White mats were composed of attached filaments resembling Beggiatoa (19.3 ± 0.5 μm, 39.0 ± 1.7 μm, and 66.9 ± 3.3 μm in diameter) and Thiothrix (4.2 ± 0.2 μm in diameter). Flexibacteria (<1 μm in diameter) were common to both mats. Beggiatoa-like filaments were morphologically similar to those attached to rocks and the byssal threads of mussels from Lucky Strike vent field on the Mid-Atlantic Ridge. Morphological comparisons were also made with typical gliding Beggiatoa from shallow seeps in Eckernförder Bucht, Baltic Sea. White mats displayed chemoautotrophic fixation of CO2 under relatively well-oxygenated laboratory conditions (maximum rate 50.2 nmol CO2/mg dry wt/h) using internal S0 or possibly S2O32− as electron donor. Photosynthesis may be limited in the Grotta Azzurra by insufficient illumination (6.3 × 10−7μ einsteins/cm2/s), with the possibility of Schizothrix living (at least in part) as a chemoheterotroph on white mats.
Chemoautotrophic fixation of CO2 by white mats is proposed as a significant source of nutrition for benthic fauna in these caves, and has been estimated as contributing 50–70 μmol CO2/m2 of mat/min, as measured under laboratory conditions.
... Preliminary investigations concerning the submarine speleology of the site have been carried out since the mid 1980s, but only after 1990 an extensive biological knowledge was achieved. Several ecological and geological studies were performed (Alvisi et al., 1994a, b;Mattison et al., 1998), particularly on the "Grotta Azzurra" (Figure 2). The cave may be separated into two topographically distinct regions: a weakly illuminated outer region and an inmost dark region (Snow Hall). ...
... Warm sulfidic water of reduced salinity enters the Snow Hall (Grotta Azzurra), from fissures in the bottom rocks, and rises above the more dense seawater to form a thermocline and chemocline as a visible boundary at a depth of about 9.5 m. The geochemistry of water samples from the Grotta Azzurra was extensively reported by Mattison et al. (1998): above and below the chemocline temperatures were 24.0 AE 0.2 and 22.8 AE 0.3, respectively; NaCl concentrations (%) were 2.6 AE 0.1 and 3.0 AE 0.1, respectively; pH values were 7.22 AE 0.02 and 8.15 AE 0.25, respectively. ...
... During the last decade both, "Grotta Azzurra" and "Grotta Sulfurea" have been investigated. Some preliminary data on the lithotrophic microflora were published (Mattison et al., 1998), and other studies were performed in order to (1) investigate the microscopic structure of bacterial mat and (2) to understand both the taxonomy and physiology of heterotrophic bacteria inside the "Grotta Azzurra" (Canganella andBianconi, 1999, 2003). The 16S rRNA genes analysis (Figure 4) showed that heterotrophic isolates were closely related to the genera Escherichia, Citrobacter, Vibrio, and Bacillus. ...
... Most available studies concern the microbial mats of the famous Grotta Azzurra and Grotta Sulfurea of Cape Palinuro, Italy (e.g. Mattison et al. 1998, Canganella et al. 2002, 2007, and more recently, marine caves and cavities of Zakynthos Island, Greece (Polymenakou et al. 2018). Microbial mats have also been reported from organic-rich sediments that accumulate in shallow marine caves at Ventimiglia (Italy), following disturbances (Nepote et al. 2017) and in a shallow cave of the north Aegean Sea (Daskalaki et al. 2018). ...
... At the interface between the marine water layer and the hydrothermal waters, a permanent chemocline is formed (Figure 25). The vault of the cave is populated by well-adapted prokaryotes (Beggiatoa-like bacteria), which form extensive mats and are responsible for oxidizing sulphides to sulphates (Mattison et al. 1998, Canganella et al. 2002, 2007. From this oxidation, sulphur bacteria draw energy for their metabolism, which is therefore chemo-lithoautotrophic. ...
Marine caves are biodiversity reservoirs and refuge habitats, harbouring rare species and living fossils. The Mediterranean Sea hosts more than 3000 caves, which are among the most studied in the world. This review aims to synthesize and update knowledge of Mediterranean marine caves. Their biota includes few obligate cave-dwelling organisms, but many cryptobiotic or crevicular (crevice-dwelling) and bathyphilic (preferring deep-water) species that secondarily colonize caves. A total of 2369 taxa have been reported from 404 caves in 15 countries, with several species new to science described in recent decades. Dramatic environmental gradients generate a zonation of the biota, with up to six faunal zones and two main biocoenoses. Biotic cover and biomass are strongly reduced inside caves, due to hydrological confinement and trophic depletion. The food web is based on suspension-feeders, but motile carnivores play a role in the importation of organic matter from outside. Lack of primary production, faunal affinities and microbial metabolism make marine caves readily accessible models of deep ocean ecosystems. Future research should focus on filling regional (e.g. south-eastern Mediterranean) and thematic (e.g. microbes, meiofauna, macroinfauna) gaps in fundamental knowledge, and on management measures. Marine caves have low ecological resilience and harbour many species of conservation interest, but are threatened by seawater warming, local human impacts and non-indigenous species.
... New research also re-examined evidence for speleogenesis in the previously studied Monte Cucco system (Galdenzi 2004;Menichetti et al. 2008), Acquasanta Terme caves (Menichetti 2008;Galdenzi et al. 2010), and the Frasassi Caves (Galdenzi et al. , 2008Galdenzi 2012;Galdenzi and Campagnoli 2015). New work also focused on other aspects of the cave environment, including the sulfidic cave ecosystem (Southward et al. 1996;Mattison et al. 1998;Sarbu et al. 2000;Forti et al. 2002), cave microbiology (Vlasceanu et al. 2000;Macalady et al. 2006Macalady et al. , 2007Jones et al. 2008Jones et al. , 2010, the depositional setting and geochemistry of gypsum deposits (Galdenzi and Maruoka 2003), quantitative measurements of corrosion rates (Galdenzi et al.1997;Mariani et al. 2007;Galdenzi 2012), and measurements of biological oxidation and degassing in the consumption of the H 2 S in the water (Jones et al. 2015). ...
... Chemoautotrophic bacteria are abundant in the sulfidic water, permitting the development of an unusually rich benthonic marine fauna inside the cave (Southward et al. 1996;Mattison et al. 1998). In the subaerial zones, the oxidation of the released H 2 S produces replacement gypsum and elemental sulfur (Forti and Mocchiuti 2004). ...
Hypogene speleogenesis is important for karstification in the Apennines because of widespread, aggressive groundwaters containing endogenic H2S and CO2. Evidence for karst processes can be found throughout the region, from solutional limestone caves to deposition of carbonate travertine. The caves are up to few tens of kilometers long and show different patterns, ranging from phreatic to almost ideal water table caves. The caves often have a maze pattern and contain large rooms, cupola roofs, blind pits, and anastomotic zones. Solutional processes prevailed in the phreatic zone, also in deep-seated conditions, but subaerial corrosion is developed as well and can play an important morphogenetic role. The main cave-forming processes are related to the H2S oxidation to sulfuric acid, a process that involves chemotrophic microbial activity, and are responsible for the diffuse deposition of replacement gypsum in subaerial conditions. The great variety of geological settings makes the Apennines a good place to study hypogene karst, and the existence of active branches in several caves also permits a direct study of the cave-forming processes and the comparison with the resultant morphologies.
... Hypogenic cave communities, devoid of any light and based on energy produced by chemoautotrophs, have been described in environments ranging from submarine caves in Italy to large caverns in Mexico (Bottrell et al. 1991;Hose et al. 2000;Mattison et al. 1998;Sarbu et al. 1996;Vlasceanu et al. 2000). In each cave, microbial mats were observed in areas with high hydrogen sulfide concentrations, and sulfide oxidation to elemental sulfur or to sulfate is the energy source for carbon fixation into biomass. ...
... In each cave, microbial mats were observed in areas with high hydrogen sulfide concentrations, and sulfide oxidation to elemental sulfur or to sulfate is the energy source for carbon fixation into biomass. Mats of sulfur-oxidizing bacteria can occur along the water-atmosphere interface in cave pools and streams (e.g., Hubbard et al. 1986) or, more commonly, at the interface between the cave conduit and the limestone cave walls where sulfide-rich groundwater seeps through the bedrock (Mattison et al. 1998). The biogeochemical reactions carried out by sulfur-oxidizing bacteria could have a significant effect on limestone dissolution and cave enlargement (Engel & Randall, 2011;Hose et al. 2000;Macalady et al. 2006;Sarbu et al. 1996;Vlasceanu et al. 2000). ...
No-mount Cave, located in Wekiwa Springs State Park in central Florida, USA, is an aphotic, submerged, freshwater cave in which large colonies of sulfur-oxidizing bacteria live in filamentous microbial mats. Upwardly discharging groundwater enters the cave from the Upper Floridan aquifer, specifically the Eocene-aged Ocala Limestone. We undertook a combined field, laboratory, and modeling study in which we sought to determine the amount of calcite dissolution attributable to the generation of protons by microbially mediated sulfide oxidation. The chemical compositions of groundwater within the limestone formation collected through a newly designed sampling device and of water in the cave conduit were used in geochemical modeling. We used the reaction-path model PHREEQCI to quantify the amount of calcite dissolution expected under various plausible scenarios for mixing of formation water with conduit water and extent of bacterial sulfide oxidation. Laboratory experiments were conducted using flow-through columns packed with crushed limestone from the study site. Replicate columns were eluted with artificial groundwater containing dissolved HS- in the absence of microbial growth. Without biologically mediated sulfide oxidation, no measurable calcite dissolution occurred in laboratory experiments and no additional amount of speleogenesis is expected as formation water mixes with conduit water in the field. In contrast, significant calcite dissolution is driven by the protons released in the biological transformation of the aqueous sulfur species. Although a range of results were calculated, a plausible amount of 158 mg Ca2+ released to conduit water per liter of groundwater crossing the formation-conduit boundary and mixing with an equal volume of conduit water was predicted. Our modeling results indicate that significant cave development can be driven by microbially mediated sulfide oxidation under these hydrogeochemical conditions.ž
Keywords: calcite dissolution, microbial sulfide oxidation, geochemical model.
DOI: 10.3986/ac.v42i2-3.663
... These waters, warm and of slightly reduced salinity, are less dense than the ambient sea water, and thus accumulate under the roof of the inner part of the Grotta Azzurra. Above the thermocline/chemocline (strongly perceptible to the diver), flourishing bacterial mats develop (Mattison & Dando, 1994;Mattison et al., 1998). ...
... It has been showed in previous papers (Southward et al., 1996;Mattison et al., 1998) that the thermocline/chemocline acts as an oxic-anoxic interface, exploited chemolithoautotrophically by sulphur-oxidising bacteria. The importance of bacterial production as a food source for at least some of the marine fauna living in the Grotta Azzurra, and particularly in the innermost Sala della Neve, has also been discussed elsewhere (Southward et al., 1996;. ...
RIASSUNTO Idrologia e bilancio idraulico di una grotta sottomarina con risorgenze sulfuree: la Grotta Azzurra di Capo Palinuro (Italia meridionale) -Nella parte più interna della Grotta Azzurra, dove si trova la principale risorgenza idrotermale, le acque sulfuree "galleggiano" sull'acqua marina, rimanendo intrappolate contro la volta della cavità e determinando la formazione di un picnoclino a 9.5-10 m di profondità. Misure effettuate con sonda multiparametrica (Idronaut Diver Monitor 101) sopra il picnoclino hanno mostrato che tali acque, rispetto a quelle sottostanti, sono più calde (+4.7 °C in media annuale), meno salate (33-34PSU) e più acide (pH = 7.2); inoltre sono pratica-mente anossiche (O 2 <1 cm 3 dm -3). I valori dei parametri fisico-chimici nelle acque sotto il picnoclino, le misure di corrente (effettuate tramite minicorrentometri ad induzione magnetica Idromar SD-4) ed il calcolo del bilancio idraulico indicano che la Grotta Azzurra, cavità di circa 46-000 m 3 complessivi, non è confinata. Questi risultati sugge-riscono che il confinamento nelle grotte sottomarine dipende dalla taglia, oltre che dalla forma: grotte grandi, seppure a fondo cieco, sono poco confinate. Il flusso idrotermale svolge un ruolo trascurabile nella circolazione generale della Grotta Azzurra, ma proba-bilmente facilita il ricambio dell'acqua sotto la volta della cavità, laddove sono stati infatti riscontrati i massimi valori di diversità e di ricoprimento della fauna sessile. 286 ABSTRACT Springs of sulphidic water inside the "Grotta Azzurra" (i.e., Blue Grotto), located at Capo Palinuro (Salerno, Italy), create a strong thermocline/chemocline at about 9.5 m depth, with the warm, less dense, sulphide-rich waters trapped under the roof of the cave and overlaying the cooler ambient seawater. This thermo-cline/chemocline is permanent, the water above it having higher temperature (+4.7 °C as a yearly average), reduced salinity (to 33-34 PSU) and pH (to 7.2), and a severe oxygen depletion (generally <lcm 3 dm -3). Current measurements indicated that no hydrological confinement exists in the Grotta Azzurra, apart from remote side branches. Water budget computation showed that complete turn-over in the cave normally requires less than one hour and only during periods of glassy cairn sea should the Grotta Azzurra undergo trophic depletion. These results suggest that confinement in submarine caves strongly depends on cave size, large caves being less confined than small caves. The outflow from the hydrothermal springs plays little role in the general water circulation inside the Grotta Azzurra, but is likely to improve local water exchange under the roof, where the most diverse and highest faunal cover has been observed.
... Here, sediments are rich in sulfides, manganese, iron oxide deposits, and clay minerals [53]. The most recent geological studies on Palinuro seamount were conducted by Cocchi et al. [68], while the only published data on the microbial communities of this site are by Mattison et al. [69]. To the best of our knowledge, these sites remain still scarcely explored. ...
Marine hydrothermal systems are a special kind of extreme environments associated with submarine volcanic activity and characterized by harsh chemo-physical conditions, in terms of hot temperature, high concentrations of CO2 and H2S, and low pH. Such conditions strongly impact the living organisms, which have to develop adaptation strategies to survive. Hydrothermal systems have attracted the interest of researchers due to their enormous ecological and biotechnological relevance. From ecological perspective, these acidified habitats are useful natural laboratories to predict the effects of global environmental changes, such as ocean acidification at ecosystem level, through the observation of the marine organism responses to environmental extremes. In addition, hydrothermal vents are known as optimal sources for isolation of thermophilic and hyperthermophilic microbes, with biotechnological potential. This double aspect is the focus of this review, which aims at providing a picture of the ecological features of the main Mediterranean hydrothermal vents. The physiological responses, abundance, and distribution of biotic components are elucidated, by focusing on the necto-benthic fauna and prokaryotic communities recognized to possess pivotal role in the marine ecosystem dynamics and as indicator species. The scientific interest in hydrothermal vents will be also reviewed by pointing out their relevance as source of bioactive molecules.
... The caves with major research efforts were Frasassi (Macalady et al., 2006Engel, 2007), Movile (Hutchens et al., 2004;Chen et al., 2009;Kumaresan et al., 2014;Bizic et al., 2020), and Lower Kane (Engel et al., 2003(Engel et al., , 2004(Engel et al., , 2010. A few individual reports on other caves and springs can be found in the literature (Mattison et al., 1998;Engel et al., 2001;Elshahed et al., 2003;Barton and Luiszer, 2005;Reigstad et al., 2011;Rossmassler et al., 2012). Among these, the microbiology of the water streamers has been the most extensively studied through molecular methods (16S rRNA clone library) but also through microscopy and culture-based experiments (Hose and Pisarowicz, 1999;Engel et al., 2004;Hamilton et al., 2015). ...
The thermal spring of Fetida Cave, a still active sulfuric acid cave opening at sea level and located in Santa Cesarea Terme, southeastern Salento (Apulia region, Southern Italy) hosts abundant floating white filaments. The white filaments were mainly composed of sulfur crystals surrounded by microbial mass of the phyla Epsilonbacteraeota, Proteobacteria, Bacteroidetes, and Patescibacteria. The most abundant genus in the white filaments collected from the waters in the innermost part of the cave dominated by sulfidic exhalations was Arcobacter. This abundance can be related to the higher concentration of sulfide dissolved in water, and low oxygen and pH values. Conversely, lower Arcobacter abundances were obtained in the filaments collected in the entrance and middle part of the cave, where sulfidic water mixes with seawater, as the cave is subjected to tides and the mixing of fresh (continental) with marine water. The geochemical analysis of water and atmospheric gases confirmed these environmental constraints. In fact, higher concentrations of H2S in the air and water were recorded closest to the spring upwelling in the innermost part of the cave, and the lower ones near the cave entrance. The metabolic versatility of Arcobacter might provide a competitive advantage in the colonization of water bodies characterized by high sulfide, low oxygen, and dynamic fluid movement.
... At the interface between the marine water layer and the hydrothermal waters, a permanent chemocline is formed (Figure 25). The vault of the cave is populated by well-adapted prokaryotes (Beggiatoa-like bacteria), which form extensive mats and are responsible for oxidizing sulphides to sulphates (Mattison et al. 1998, Canganella et al. 2002, 2007. ...
Marine caves are biodiversity reservoirs and refuge habitats, harbouring rare species and living fossils. The Mediterranean Sea hosts more than 3000 caves, which are among the most studied in the world. This review aims to synthesize and update knowledge of Mediterranean marine caves. Their biota includes few obligate cave-dwelling organisms, but many cryptobiotic or crevicular (crevice-dwelling) and bathyphilic (preferring deep-water) species that secondarily colonize caves. A total of 2369 taxa has been reported from 350 caves in 15 countries, with several species new to science described in recent decades. Dramatic environmental gradients generate a zonation of the biota, with up to six faunal zones and two main biocoenoses. Biotic cover and biomass are strongly reduced inside caves, due to hydrological confinement and trophic depletion. The food web is based on suspension feeders, but motile carnivores play a role in the importation of organic matter from outside. Lack of primary production, faunal affinities, and microbial metabolism make marine caves readily accessible models of deep ocean ecosystems. Future research should focus on filling regional (e.g. southeastern Mediterranean) and thematic (e.g. microbes, meiofauna, macroinfauna) gaps in fundamental knowledge, and on management measures. Marine caves have low ecological resilience and harbour many species of conservation interest, but are threatened by seawater warming, local human impacts, and non-indigenous species.
... All caves open at sea level at the foot of a limestone cliff (Fig 1) [33]. Santa Cesarea Terme and Capo Palinuro (Tyrrhenian coast South of Naples) represent unique examples of still active sulfuric acid cave systems, which are open at sea level [34]. Copious microbial communities are visible as biofilms/deposits in the deeper zone of the cave (in correspondence of the H 2 S-rich rising water). ...
Fetida Cave is an active sulfuric acid cave influenced by seawater, showing abundant microbial communities that organize themselves under three main different morphologies: water filaments, vermiculations and moonmilk deposits. These biofilms/deposits have different cave distribution, pH, macro-and microelement and mineralogical composition, carbon and nitrogen content. In particular, water filaments and vermiculations had circumneutral and slightly acidic pH, respectively, both had abundant organic carbon and high microbial diversity. They were rich in macro-and microelements, deriving from mineral dissolution, and, in the case of water filaments, from seawater composition. Vermiculations had different color, partly associated with their mineralogy, and unusual minerals probably due to trapping capacities. Moonmilk was composed of gypsum, poor in organic matter, had an extremely low pH (0-1) and low microbial diversity. Based on 16S rRNA gene analysis, the microbial composition of the biofilms/deposits included autotrophic taxa associated with sulfur and nitrogen cycles and biomineralization processes. In particular, water filaments communities were characterized by bacterial taxa involved in sulfur oxidation and reduction in aquatic, aphotic, microaerophilic/anoxic environments (Campylobacterales, Thiotrichales, Arenicel-lales, Desulfobacterales, Desulforomonadales) and in chemolithotrophy in marine habitats (Oceanospirillales, Chromatiales). Their biodiversity was linked to the morphology of the water filaments and their collection site. Microbial communities within vermiculations were partly related to their color and showed high abundance of unclassified Betaproteobacteria and sulfur-oxidizing Hydrogenophilales (including Sulfuriferula), and Acidiferrobacterales (including Sulfurifustis), sulfur-reducing Desulfurellales, and ammonia-oxidizing Planctomy-cetes and Nitrospirae. The microbial community associated with gypsum moonmilk showed PLOS ONE | https://doi.org/10.1371/journal.
... Their waters have temperature of 18-25°C and pH of 7.22-8.15, and are colonized by stream biofilms (Mattison et al., 1998;Canganella et al., 2007). Grotta a Ovest di Cala Fetente, and Grotta di Punta Galena show fossil signatures of sulfuric acid activities (Forti and Mocchiutti, 2004). ...
Many active and inactive hypogene sulfuric acid cave systems are known along the Apennines, Italy. The Cavallone-Bove cave system is located in the external part of the central Apennine Chain, in the Majella Massif, and opens at 1470 m asl along the Taranta Gorge (South of Chieti). The presence in these caves of peculiar geomorphological features, such as feeders, rising channels, megacusps, cupolas, and replacement pockets, offers evidence of rising acidic fluids. The secondary mineral deposits, including meter-size white gypsum deposits, alunite, jarosite, black layers of iron‑manganese oxides and hydroxides, along with a rare association of authigenic rutile-ilmenite minerals indicate a sulfuric acid origin. Stable isotope analyses of sulfates further confirm a sulfuric acid speleogenetic (SAS) origin of these minerals and, in general, of the whole cave system, with H 2 S coming from the bacterial sulfate reduction of deep-seated Triassic evaporites interacting with hydrocarbons. Alunite dating demonstrates this water table SAS cave to have been active at least until 1.52 ± 0.28 Ma. All the evidence suggests that Cavallone-Bove is an ancient sulfuric acid karst system that was uplifted <1 km above pre-existing base level. The age of speleogenesis further suggests that tectonic uplift of this area was as high as 670 m My ⁻¹ over the last 1.5 Ma.
... Their waters have temperature of 18-25°C and pH of 7.22-8.15, and are colonized by stream biofilms (Mattison et al., 1998;Canganella et al., 2007). Grotta a Ovest di Cala Fetente, and Grotta di Punta Galena show fossil signatures of sulfuric acid activities (Forti and Mocchiutti, 2004). ...
In Italy, especially along the Apennine Chain, numerous active and inactive sulfuric acid speleogenetic (SAS) caves have been documented in the last two decades. Here we present an overview of these peculiar hypogene systems, illustrating their main geomorphological and mineralogical features, and the microbial signatures observed in the active underground environment. SAS caves are widely distributed in the northern and central Apennines, whereas they are less abundant in the southern Apennines, in the Apulian foreland, in Sicily and in Sardinia. Their location is significantly influenced by lithological and structural rock properties, as they occur in carbonate areas where acidic fluids, deriving from the interactions with deep-seated sulfates and/or sulfides, rise through deeply rooted geological structures. Geomorphological observations demonstrated sub-horizontal maze passages to be one of the most favorite arrangements for SAS caves, whereas gypsum, sulfur and alunite supergroup minerals are the most typical sulfuric acid by-products. The δ ³⁴ S results demonstrated the deep-seated H 2 S sources to be mainly related to the interaction between Triassic evaporites and hydrocarbons.
... However, insights into their microbiology are limited. Specifically, only 6 marine caves have been investigated regarding their microbial communities, namely, Grotta Azzurra and Grotta Sulfurea on the Tyrrhenian coasts of Italy (Mattison et al., 1998;Canganella et al., 2002;Maugeri et al., 2010); Gymnasium, Granchi and Mazzere caves on the Ionian coast of Sicily (Guido et al., 2012(Guido et al., , 2013(Guido et al., , 2014(Guido et al., , 2016Sanfilippo et al., 2015); and Kakoskali cave in Cyprus . However, only the former two have been investigated for their microbiota, using molecular techniques, while studies on the other three caves involved the morphological identification of microbial structures. ...
Mediterranean marine caves remain largely unexplored, while particularly limited information is available about microbial life in these unique environments. This study is a preliminary assessment of the composition of the active anaerobic microbial community colonizing the walls of newly explored systems of underwater caves and small cavities in Zakynthos Island. The interior of these caves is densely coated with egg-shaped, foam-shaped and filamentous biological structures that are characterised by a strong odour of hydrogen sulphide gas. A total of twelve structures scrapped from cave rocks were subjected to anaerobic cultivation for up to 208 days. Strong to moderate methanogenesis was observed in two different types of egg-shaped structures and one foam-like structure. Interestingly, this was observed in experiments that were performed at room temperature (i.e. 25 o C), which is substantially lower than those typically considered optimum for methane production (e.g. 35 o C). An analysis of the 16S rRNA genes revealed a clear dominance of archaea and bacteria closely related to known methane producers and sulphate reducers, including members of the families Methanomicrobiaceae, Desulfobulbaceae, Desulfobacteraceae, Desulfuromonaceae, Campylobactera-ceae, Marinifilaceae, Clostridiaceae, Incertae Sedis-Family I & II. These results show that Mediterranean marine caves can host members of archaea and bacteria with potential biotechnological interest that deserves further investigation.
... The extreme and confined conditions of the caves are ideal for microbial and numerous microorganisms growth, including heterotrophic and phototrophic bacteria, which have been described also from various terrestrial caves (Cubbon 1976). Microbial mats and biofilms, dominated by bacteria or cyanobacteria, have been described from aerobic (Abdelahad 1989;Jones 1995) and anaerobic limestone or dolostone caves (Sarbu et al. 1996;Mattison et al. 1998). Although these microbial mats and biofilms are commonly associated with various minerals, including clays and carbonates, few recent studies have been focused on the role of microorganisms, especially bacteria, in the formation of authigenic marine cave minerals (Guido et al. 2013(Guido et al. , 2016a. ...
The biostalactites from the Kakoskali cave in Cyprus represent a new example of the complex biotic relationships between skeletal organisms and microbial communities in building bioconstructions of cryptic marine environments. Biostalactites are mainly constituted of polychaetes of the family Serpulidae and, to a lesser degree, foraminifers and bryozoans. Within the skeletal framework of these organisms, two types of microcrystalline calcite (micrite) have been recognized: autochthonous and detrital micrite. The autochthonous fraction is syndepositionally lithified and occurs as clotted peloidal and, subordinately, aphanitic (structureless) textures, suggesting the presence of heterotrophic microbial activities thriving on decaying metazoan organic matter. This fraction is limited to the protected portions of the bioconstructions, especially in the inner and lower parts. The presence of iron and manganesiferous oxidizing bacteria is suggested by the deposition of ferromanganesiferous crusts and Frutexites-like structures. These microbial-induced biomineralizations are the main evidence of carbonatogenetic and Fe–Mn, autotrophic and chemoheterotrophic, bacterial activities. The Kakoskali cave is frequently visited by divers who, during their immersions, resuspend the fine bottom sediment, which later covers the surface of the bioconstructions, disturbing the delicate equilibrium of the biotic association. This perturbation, which is also caused by strong waves and currents, during winter months, reflects on the bioconstruction morphologies, community composition, and colonization pattern. Bioconstructions exhibit an upper smooth surface, produced by few taxa (e.g., polychaetes, foraminifers), hosting a low number of living individuals, and a lower comparably rough surface, colonized by a more abundant community showing a higher species richness. The ratio surface roughness/smoothness is related to micrite sediment type: the upper part is mainly characterized by loose detrital micrite while the internal and lower parts by syndepositional cemented autochthonous micrite.
... Aside from the CO 2 in the air or dissolved in water, other compounds such as methane are used by bacteria for organic matter synthesis, while the necessary energy is provided by oxidation of compounds such as H 2 S, CH 4 , or NH 4 + . Nevertheless, in the majority of such hypogenic caves (the submarine Grotta Azurra, Cape Palinuro, and Frasassi Caves, Italy; the terrestrial Cesspool Cave, Virginia, USA; Lower Kane Cave, Wyoming, USA; Lechuguilla Cave and Carlsbad Cave, New Mexico, USA; Cueva de Villa Luz, Mexico; Cuup-Coutunn Cave, Turkmenistan), the ecosystems are only partially based on chemosynthesis, with the main nutrients still coming from an exogenous origin (Barton and Luiszer 2005;Boston et al. 2006;Campbell et al. 2006;Canganella et al. 2002;Engel 2007;Engel et al. 2001Engel et al. , 2009Forti et al. 2002;Hose et al. 2000;Hubbard et al. 1986;Macalady et al. 2006Macalady et al. , 2007Mattison et al. 1998;Meisinger et al. 2007;Porter et al. 2008Porter et al. , 2009. In contrast, Movile Cave (Peștera Movile, Romania) and the more recently discovered Ayyalon Cave (Israel) are completely isolated from the surface (Sarbu 2000;Sarbu et al. 1994Sarbu et al. , 1996Por 2007;Por et al. 2013) and entirely dependent on chemosynthesis, with the organic matter being synthesized in situ. ...
Movile Cave, a unique groundwater ecosystem in southern Romania, was discovered in 1986. This chemoautotrophic cave contains an abundant and diverse fauna with terrestrial and aquatic invertebrate communities, including 33 endemic species. Since its discovery, studies have focused mainly on cave chemoautotrophic bacteria, while the microfungal community has been largely neglected. In this study, we determined the microfungal species living on various substrates in Movile Cave and compared this spectrum with the mycobiota detected outside the cave (outside air-borne and soil-borne microfungi). To investigate all of the niches, we collected samples for two consecutive years from the dry part of the cave (cave air and sediment, corroded limestone walls, isopod feces, and isopod and spider cadavers) and from the post-siphon part of the cave, i.e., Airbell II (sediment and floating microbial mat). A total of 123 microfungal species were identified from among several hundred isolates. Of these, 96 species were only detected in the cave environment and not outside of the cave, while 90 species were from the dry part of the cave and 28 were from Airbell II. The most diverse genera were Penicillium (at least 18 species) and Aspergillus (14 species), followed by Cladosporium (9 species). Surprisingly, high CFU counts of air-borne microfungi were found inside the cave; they were even higher than outside the cave during the first year of investigation.
... Instead, its ecosystem is based on chemoautotrophic microbial mats (Sarbu et al. 1996). Other examples of sulfide-based microbial communities in caves have been reported throughout the world: in Cueva de Villa Luz in Tabasco, Mexico (Hose and Pisarowicz 1997); in submarine caves at Cape Palinuro, Italy (Mattison et al. 1998); and in Parker Cave, Kentucky Thompson and Olson 1988). ...
Sulphur River in Parker Cave, Kentucky receives sulfurous water (11-21 mg sulfide/L) from the Phantom Waterfall and contains a microbial mat composed of white filaments. We extend a previous morphological survey with a molecular phylogenetic analysis of the bacteria of the microbial mat. This approach employs DNA sequence comparisons of small subunit ribosomal RNA (SSU rRNA) genes obtained from the mat with those from an extensive database of rRNA sequences. Many of SSU rRNA gene clones obtained from the mat are most similar to rRNA sequences from sulfur-oxidizing bacteria (Thiothrix spp., Thiomicrospira denitrificans, and "Candidatus Thiobacillus baregensis"). The Sulphur River SSU rRNA gene clones also show specific affiliations with clones from environmental surveys of bacteria from deep-sea hydrothermal vent communities and subsurface microcosms. Affiliations with sequences from bacteria that are known to have the ability to obtain energy for CO2 fixation from the oxidation of inorganic compounds (chemoautotrophs), in combination with the environmental conditions surrounding the microbial mat, indicate that chemoautotrophic metabolism of bacteria in this mat may contribute to the biomass of Sulphur River. Cave communities, such as the one identified in Sulphur River, provide sites to study such relatively autonomous chemoautotrophic communities that are much more accessible than similar communities associated with deep-sea hydrothermal vents. Subsurface microbiology and the contribution of microbial activity on cave development are also discussed.
... Their ecophysiological flexibility allows the Beggiatoaceae to colonize a wide spectrum of freshwater and marine environments; Beggiatoaceae can be found in a wide range of habitats, including organic-rich, coastal marine sediments (Jørgensen 1977;Klas 1937;Mussmann et al. 2003;Rosenberg and Diaz 1993); benthic microbial mats (Teske and Stahl 2002) salt marshes ; eutrophic, oxygen-depleted bays (Graco et al. 2001;Vallius 2006); marine oxygen-minimum zones (Schmaljohann et al. 2001); oxygen-depleted marine basins (Williams and Reimers 1983); geothermally active submarine caves (Mattison et al. 1998); hydrothermal vents Nelson et al. 1989); cold sulfide seeps (Sassen et al. 1994); and hydrocarbon seeps (Larkin et al. 1994). Freshwater habitats include sulfur springs (Uphof 1927;Caldwell et al. 1975;Nelson and Castenholz 1981b;Fukui et al. 1999); freshwater ditches, puddles, wetlands, and lake sediments (Koppe 1924;Pringsheim 1964;Scotten and Stokes 1962;Strohl and Larkin 1978a); terrestrial salt springs (Kolkwitz 1918); and sulfidic cave streams (Macalady et al. 2006(Macalady et al. , 2008. ...
The family Beggiatoaceae contains a wide range of morphologically conspicuous, aerobic, or nitrate-dependent sulfide-oxidizing bacteria that span the range from obligate sulfur-based chemolithoautotrophy to heterotrophic growth supplemented by sulfur oxidation. The Beggiatoaceae are the model organisms for the concept of chemolithotrophy, developed by Sergei Winogradsky during his postgraduate studies using natural populations of filamentous freshwater Beggiatoaceae collected in sulfur springs. Since the metabolism of the Beggiatoaceae requires access to reduced sulfur species and oxidants such as oxygen or nitrate, these bacteria thrive in microbial mats, surficial sediments, and sediment-water interfaces where these electron donors and acceptors coexist and can be intercepted for microbial energy generation before gradual abiotic sulfide oxidation sets in. All Beggiatoaceae have the ability to oxidize sulfide to elemental sulfur that is stored as intracellular sulfur globules, which make the cells highly refractory and conspicuous with the unaided eye and under the microscope. This characteristic, together with the absence of photosynthetic pigments, has led to their traditional designation as members of the colorless sulfur bacteria, in contrast to the photosynthetic purple and green sulfur bacteria or the cyanobacteria. The white, yellow, or occasionally orange color of the Beggiatoaceae, their frequently filamentous or chain-like morphology, their growth pattern in flocs and mats on sediment surfaces, and their large cell size and capacity for storing several different compounds intracellularly have made these organisms fascinating research targets. Extensive microscopic and morphological surveys have focused on these bacteria since the late nineteenth and early twentieth century. To a surprising extent, early microscopic and morphological observations on large, morphologically conspicuous sulfur bacteria can be reintegrated into the emerging molecular and phenotypic taxonomy of the Beggiatoaceae today. © 2014 Springer-Verlag Berlin Heidelberg. All rights are reserved.
... Le risorgenze convogliano acque cariche di sulfuri originatesi più profondamente nella crosta terrestre (Stüben et al., 1997): queste acque, essendo calde e non salate e quindi meno dense, 'galleggiano' sull'acqua marina, fluendo contro la volta della cavità, mentre all'interfaccia tra acque marine e acque idrotermali si forma una chemioclino permanente (Figura 5). Sulla roccia della volta si sviluppano cospicui tappeti di solfobatteri (Beggiatoa) che si occupano di ossidare i sulfuri in solfati (Mattison et al., 1998). Da questa ossidazione i solfobatteri traggono energia per il loro metabolismo, che è pertanto definibile chemio-lito-autotrofo. ...
... Thiomargarita nelsonii" and other large, colorless SOB with cyanobacteria ( MacGregor et al., 2013b). This hypothesis is further supported by the observation that large colorless SOB often occur in the same environment as cyanobacteria, where they can form cohesive microbial mats (Larkin and Strohl, 1983;Garcia-Pichel et al., 1994;Mattison et al., 1998). ...
Deep-sea hydrothermal vent systems are highly productive ecosystems, where reduced energy sources fuel complex communities of microorganisms, invertebrates and vertebrates. Since decades the oxidation of methane, hydrogen and inorganic sulfur compounds has been extensively studied. However, the role of inorganic nitrogen and of organic compounds as energy source has been investigated only scarcely in hydrothermal fluids, in particular at the sea floor, where hydrothermal fluids exit subsurface. The aim of my thesis was to shed light on these under-investigated topics. In my first project I studied nitrification and the involved microbes that are associated with large, nitrate-respiring and sulfur-oxidizing bacteria (SOB) of the genus Beggiatoa. These SOB formed mats and covered sulfide- and ammonia-rich hydrothermal sediments in the Guaymas Basin. In these mats, nitrification rates were measured using 15N-labeled ammonium. With up to 605 Mikromol N l-1 mat d-1 the nitrification rates were the highest measured for a deep-sea ecosystem. Diversity and quantitative PCR of the ammonia monooxygenase subunit A gene (amoA) indicated association of ammonia-oxidizing archaea (AOA) and bacteria (AOB) with Beggiatoa mats. In line with this, single cells of AOB and potentially ammonia-oxidizing thaumarchaotes were attached to narrow Beggiatoa-like filaments. Nitrite oxidizing bacteria were also found. Nitrifying bacteria associated with Beggiatoa mats that respire nitrate to ammonium (DNRA) could display a syntrophic consortium that internally cycle nitrogen and thereby reduce loss of bioavailable nitrogen. However, it is not clear whether large SOB in general respire nitrate also to dinitrogen. Therefore, I analyzed the genetic potential of the large SOB "Candidatus Thiomargarita nelsonii" , a close relative of Beggiatoa. The comparison to four other Beggiatoaceae identified genes for both denitrification and DNRA in "Ca. T. nelsonii" and three other Beggiatoaceae. This indicates that both pathways are widely distributed among large SOB and questions the hypothesis of internal N-cycling in mats of large SOB. In my third project I investigated the microbial consumption of organic compounds that are produced in hydrothermal systems. In particular I studied acetate-assimilating heterotrophic communities in the diffuse fluids (temperature range of 4-72 degree Celsius) of two rock-hosted hydrothermal systems. 16S rRNA gene-based diversity analysis and fluorescence in situ hybridization (FISH) showed that either Gammaproteobacteria or Epsilonproteobacteria rapidly grew during short-term (8-12 h) incubations with 13C-acetate. Single cells of both groups incorporated 13C-acetate as shown by nanoSIMS. Marinobacter spp. and a novel group among the Nautiliales could be heterotrophs in these systems. These are potential r-strategists that quickly respond to the fluctuating availabilities of energy sources in hydrothermal fluids.
... are non-gliding and do not establish mat structures, but rather gelatinous streamers or bulking sludge in sewage treatment plants (van Veen et al. 1978;Larkin and Strohl 1983;Nielsen et al. 2000). On a few occasions dense Thiothrix growth has been reported to occur in communities from seep areas or artesian wells, but mass occurrence is rarely encountered in natural aquatic systems (Jacq et al. 1989;McGlannan and Makemson 1990;Mattison et al. 1998;Pimenov et al. 2000). Other conspicuous mass occurrences of sulfide-oxidizing bacteria include a recently described vibrioid, Arcobacter sp., which forms voluminous mats of flocculent material composed of irregular sulfur filaments (Taylor and Wirsen 1997;Wirsen et al. 2002). ...
... are non-gliding and do not establish mat structures, but rather gelatinous streamers or bulking sludge in sewage treatment plants (van Veen et al. 1978;Larkin and Strohl 1983;Nielsen et al. 2000). On a few occasions dense Thiothrix growth has been reported to occur in communities from seep areas or artesian wells, but mass occurrence is rarely encountered in natural aquatic systems (Jacq et al. 1989;McGlannan and Makemson 1990;Mattison et al. 1998;Pimenov et al. 2000). Other conspicuous mass occurrences of sulfide-oxidizing bacteria include a recently described vibrioid, Arcobacter sp., which forms voluminous mats of flocculent material composed of irregular sulfur filaments (Taylor and Wirsen 1997;Wirsen et al. 2002). ...
... These are chemoautotrophic bacteria that have been proposed as major primary producers at deep-sea vents. In addition, microbial mats found in submarine caves of dolomitized limestone that contain hydrothermal sul dic springs, located at Cape Palinuro, Italy, have been shown to be capable of chemoautotrophic activity under laboratory conditions (Mattison et al. 1998). ...
Acidic biofilms present on cave walls in the sulfidic region of the Frasassi Gorge, Italy, were investigated to determine their microbial composition and their potential role in cave formation and ecosystem functioning. All biofilm samples examined had pH values Thiobacillus and Sulfobacillus. An acid-producing strain of Thiobacillus sp. also was obtained in pure culture. Stable isotope ratio analysis of carbon and nitrogen showed that the wall biofilms are isotopically light, suggesting that in situ chemoautotrophic activity plays an important role in this subsurface ecosystem.
... Whilst most caves and karst features are considered to be formed as a result of abiotic dissolution of carbonate rocks by infiltrating CO 2 saturated rainwater, this is not the only process operating in cave systems (Egemeier, 1981;Palmer, 1991). Several recent studies have shown that sulphide can be oxidised to sulphuric acid either abiotically by reacting with oxygen-rich water or biotically by chemoautotrophic sulphur-oxidising bacteria (Mattison et al., 1998;Vlasceanu et al., 1997Vlasceanu et al., , 2000. In the South Andros Black Hole most of the biogenically generated sulphide is consumed by the purple sulphur bacteria as e À donor in anoxygenic photosynthesis but the presence of a thin white veil of bacteria at the upper boundary between the sulphidic micro-oxic saline layer and the oxic brackish water mass is indicative of the presence of mat forming sulphuroxidising bacteria such as Beggiatoa. ...
Black holes are vertical cave systems, which have no known lateral passages and form in the interior stable regions of the larger Bahamian islands. They are found where the land is transitional between submerged and dry land, not dissimilar to saltmarsh environments. Most Black Holes are located in the central to western side of the island of South Andros in the Bahamas, although one has been found on the northern transitional shore of Grand Bahama Island. The water in these holes appears black in colour due to the presence of a 1m thick microbial layer located within the upper third of the water column (18–19m) at the boundary between the oxic low salinity upper water mass and the denser anoxic saline water layer. The boundary between the two water masses is characterised by sharp discontinuities in physico-chemical gradients: salinity increased from 12 to 35psu; temperature from 29°C to 36°C; pH decreased from pH 8.6 to 6.45 and dissolved O2 from 6mg/l to 107 viable cells/ml. Calculations reveal that this layer of anoxygenic phototrophic bacteria, in the South Andros Black Hole may have a biomass content of approximately 5.06 ton dry weight.
... Numerous studies deal with symbiotic associations of bacteria with the vent fauna (Nelson & Fisher 1995, Jeanthon 2000, Imhoff et al. 2003, and with the isolation and characterization of (hyper)thermophilic bacteria and archaea from extremely hot vents (Baross & Deming 1995, Reysenbach et al. 2000. Many bacterial isolates characterized from hydrothermal vent environments are chemolithoautotrophic bacteria representing initial settlement on hard substrates or within the sediment (Gunderson et al. 1992, Gugliandolo & Maugeri 1993, Moyer et al. 1994, Muyzer et al. 1995, Mattison et al. 1998, Taylor et al. 1999. In more recent studies, 16S rDNA-based approaches have also been applied to study the bacterial diversity at hydrothermal habitats, such as hydrothermally influenced Aegean sediments, and vent chimneys on the ABSTRACT: We determined key chemical parameters and thiosulfate oxidation in low-temperature hydrothermal fluids from the North Fiji Basin. ...
We determined key chemical parameters and thiosuffate oxidation in low-temperature hydrothermal fluids from the North Fiji Basin. In addition, the bacterial diversity (with the main emphasis on sulfur-oxidizing bacteria) was investigated. The hydrothermal fluids had low concentrations of sulfide (up to 50.0 muM) and increased counts of both total bacteria and sulfur-oxidizing bacteria compared to ambient seawater. Pure cultures of bacteria were isolated from these fluids on media suited for autotrophic, and potentially heterotrophic, sulfur-oxidizing bacteria. Evidence for the abundance of alpha- and gamma-Proteobacteria was obtained from identification of isolated pure cultures. A large number of 16S rDNA sequences of these groups were retrieved from environmental DNA. Representatives of the Cytophaga-Flavobacterium phylum were found by denaturing gradient gel electrophoresis (DGGE) and 16S rDNA sequence information of DGGE bands, although these bacteria could not be isolated with the media used in this study. Evidence for the presence of chemolithoautotrophic sulfur-oxidizing bacteria was found by analysis of environmental DNA, using 16S rDNA-specific primers of various groups of chemotrophic sulfur bacteria. They were isolated in low numbers compared to chemoheterotrophic and mixotrophic sulfur-oxidizing bacteria. In addition, the formation of tetrathionate as major oxidation product of thiosulfate added to hydrothermal fluid samples and to pure cultures of new isolates indicates the importance of chemoheterotrophic sulfur-oxidizing bacteria within the warm vent waters investigated during this study.
... The recovery of abundant 16S rDNA clones from Lechuguilla Cave ferromanganese deposits that affiliate with mesophilic Crenarchaeota and Euryarchaeota was unexpected and indicates the presence of several new groups of Archaea only distantly related to other known organisms. This represents the first published evidence for the presence of mesophilic Crenarchaeota and 'Group 2' Euryarchaeota (DeLong et al., 1994) in caves and the second published report of Archaea in caves (Mattison et al., 1998). There has been one additional report of sequences from these groups obtained from Movile Cave, Romania (L. ...
... Submarine caves within limestone bedrock are known to occur along the Tyrrhenian coast, some of which were formed by and contain active sulphide-rich springs that sustain a trophic chain dominated by prokaryotes. The best examples are found at Capo Palinuro in southern Italy ( Fig. 5.2 ), where sulphide-containing warm springs support dense Beggiatoa -like bacterial mats and other chemoautotrophic prokaryotes (Maugeri et al. 2010 ) that in turn sustain some metazoans including sponges, cnidarians and polychaetes, often of abnormally large size (Alvisi et al. 1994 ;Morri et al. 1994 ;Mattison et al. 1998 ;Canganella et al. 2007 ;Southward et al. 2009 ;Dando 2010 ). Many metazoans sharing this habitat are covered by bacterial fi laments (Southward et al. 2009 ). ...
The Mediterranean Sea contains a vast spectrum of chemosynthetic habitats from shallow marine to bathyal depths. These habitats (hydrothermal vents, cold seeps, reducing sediment) are home to bacteria and archaea acting as primary producers using the energy obtained by oxidizing reducing compounds in fluids (e.g., H2S and hydrocarbons such as CH4) to synthesize organic matter. Such sites may make a large microbial biomass available to consumers and promote the development of complex symbiotic relationships between prokaryotes and hosting eukaryotes. Shallow water (200 m) with also metazoans with chemoautotrophic symbionts are present at various sites in the Mediterranean, encompassing both cold seeps and hydrothermal vents. Cold seeps are diffuse and geologically diverse, and comprise mud volcanoes, brine pools and active pockmark fields, whose reducing environments are often exploited by endemic chemosymbiotic metazoans, including bivalves and siboglinid polychaetes. Such environments are clustered in the Eastern Mediterranean (Nile Deep Sea Fan, Anaximander mud volcano field, Olimpi mud volcano field, Eratosthenes Seamount, Calabrian Arc, Marmara deep fault systems) but equally occur in the Strait of Sicily, Adriatic, Tyrrhenian and Alboran Seas. Deep hyperhaline anoxic basins occur in the Eastern Mediterranean and even host metazoans that live in anoxic conditions. Deep-water hydrothermal vents characterized by microbial communities and metazoans (siboglinid polychaetes) are documented so far only from some Tyrrhenian seamounts (Marsili, Palinuro) and Aegean submerged volcanic craters (Santorini, Kolumbo). The geo-biological relevance of such complex habitats often situated in the high seas, calls for an international effort towards the implementation of proper protection and sustainable management.
... One distinguishing characteristic of habitats where Beggiatoa is found appears to be the presence of detectable free sulfide. Typical habitats include cold seeps Kalanetra et al., 2003), upwelling areas with high organic input (Brü chert et al., 2003), whale carcasses, sulfidic springs (Martinez et al., 1997;Mattison et al., 1998), hydrothermal vents (Nelson et al., 1989) and hypersaline mats (Garcia-Pichel et al., 1994;Jonkers et al., 2003), all of which have steep sulfide gradients. High temperatures seem to exclude Beggiatoa as they are not reported from sulfidic hot springs. ...
The ecological niche of nitrate-storing Beggiatoa, and their contribution to the removal of sulfide were investigated in coastal sediment. With microsensors a clear suboxic zone of 2–10 cm thick was identified, where neither oxygen nor free sulfide was detectable. In this zone most of the Beggiatoa were found, where they oxidize sulfide with internally stored nitrate. The sulfide input into the suboxic zone was dominated by an upward sulfide flux from deeper sediment, whereas the local production in the suboxic zone was much smaller. Despite their abundance, the calculated sulfide-oxidizing capacity of the Beggiatoa could account for only a small fraction of the total sulfide removal in the sediment. Consequently, most of the sulfide flux into the suboxic layer must have been removed by chemical processes, mainly by precipitation with Fe2+ and oxidation by Fe(III), which was coupled with a pH increase. The free Fe2+ diffusing upwards was oxidized by Mn(IV), resulting in a strong pH decrease. The nitrate storage capacity allows Beggiatoa to migrate randomly up and down in anoxic sediments with an accumulated gliding distance of 4 m before running out of nitrate. We propose that the steep sulfide gradient and corresponding high sulfide flux, a typical characteristic of Beggiatoa habitats, is not needed for their metabolic performance, but rather used as a chemotactic cue by the highly motile filaments to avoid getting lost at depth in the sediment. Indeed sulfide is a repellant for Beggiatoa.Keywords: microsensor, chemotaxis, geochemistry, suboxic zone, sulfate reduction, nitrate reduction
... The bacteria were mainly an attached form of Beggiatoa, with a mean trichome width of 39.1 F 7.0 (S.D.) Am and a length of 3664 F 381 (S.D.) Am (n = 100). The trichomes had a somewhat swollen basal end towards the attachment point and were similar to the similar size group of Beggiatoa found in the Grotta Azzurra submarine cave which contained a geothermal spring (Mattison et al., 1998). ...
D. João de Castro seamount has an elevation of 1000 m and is located between the islands of Terceira and São Miguel, Azores, on the hyper-slow spreading Terceira Rift. The summit of the seamount shoals to 13 m below sea level and has hydrothermal vents at a depth of 20 m. This is the first vent system to be described on a hyperslow spreading centre. Gas discharging from the vents is dominated by CO 2 (90%) with lesser H 2 S, H 2 and CH 4 . Two distinct vent areas were identified that had different physical and chemical characteristics. The white area had vent orifices with white bacterial mats, while the yellow area had yellowish coloured vent openings. Vents in the white area had lower temperatures (V 43 8C), but higher concentrations of H 2 S, CH 4 and H 2 . Beggiatoa sp. was found in this area. The yellow area had vent temperatures up to 63 8C. No typical hydrothermal vent fauna was found at these vents. The macro species present were similar to those found in coastal and seamount areas of the Azorean Archipelago. There was evidence for the presence of deeper vents on the flanks of the D. João de Castro seamount, at depths between 150–400 m. D 2005 Published by Elsevier B.V.
In 2016, IODP‐ICDP Expedition 364 recovered an 829‐meter‐long core within the peak ring of the Chicxulub impact crater (Yucatán, Mexico), allowing us to investigate the post‐impact recovery of the heat‐sterilized deep continental microbial biosphere at the impact site. We recently reported increased cell biomass in the impact suevite, which was deposited within the first few hours of the Cenozoic, and that the overall microbial communities differed significantly between the suevite and the other main core lithologies (i.e., the granitic basement and the overlying Early Eocene marine sediments; Cockell et al., 2021). However, only seven rock intervals were previously analyzed from the geologically heterogenic and impact‐deformed 587‐m‐long granitic core section below the suevite interval. Here, we used 16S rRNA gene profiling to study the microbial community composition in 45 intervals including (a) 31 impact‐shocked granites, (b) 7 non‐granitic rocks (i.e., consisting of suevite and impact melt rocks intercalated into the granites during crater formation and strongly serpentinized pre‐impact sub‐volcanic, ultramafic basanite/dolerite), and (c) 7 cross‐cut mineral veins of anhydride and silica. Most recovered microbial taxa resemble those found in hydrothermal systems. Spearman correlation analysis confirmed that the borehole temperature, which gradually increased from 47 to 69°C with core depth, significantly shaped a subset of the vertically stratified modern microbial community composition in the granitic basement rocks. However, bacterial communities differed significantly between the impoverished shattered granites and nutrient‐enriched non‐granite rocks, even though both lithologies were at similar depths and temperatures. Furthermore, Spearman analysis revealed a strong correlation between the microbial communities and bioavailable chemical compounds and suggests the presence of chemolithoautotrophs, which most likely still play an active role in metal and sulfur cycling. These results indicate that post‐impact microbial niche separation has also occurred in the granitic basement lithologies, as previously shown for the newly formed lithologies. Moreover, our data suggest that the impact‐induced geochemical boundaries continue to shape the modern‐day deep biosphere in the granitic basement underlying the Chicxulub crater.
Microbialites are common carbonate structures in cryptic niches of marine environments throughout geological time. In this research we compare the microbialites of small bioconstructions (biostalactites) of modern submarine caves of Sicily with those developed in small crypts of Carnian patch reefs of the Dolomite Mountains (Heiligkreuz Formation, Alpe di Specie) using Raman spectroscopy, a method that allows in situ determination of the organic content of microbial components. This methodology partly solves the uncertainty of geomicrobiological studies that use bulk measurements (i.e., biomarker analyses), which make it difficult to associate mineral precipitates with a specific microbial process. In the modern marine caves, the complex biotic relationships among skeletal organisms (mainly serpulids) and microbial communities produced biostalactites in which microbially induced biomineralization is the consequence of autotrophic and chemoheterotrophic bacterial activities. Sulfate-reducing bacteria, fed by metazoan organic matter, flourish in millimetric oxygen-depleted cavities of the skeletal framework, and induce autochthonous micrite deposition and early stabilization of the biostalactites. Similar processes have been interpreted to induce the deposition of the microbialites in the Upper Triassic patch reefs of the Dolomites. These small shallow water reefs, made up mainly of scleractinian corals, sponges and red algae, hold a skeletal framework rich in millimeter- to centimeter-size cavities, ideal cryptic niches for growth of microbial communities. Specific sulfate-reducing bacteria biomarkers are first identified using bulk measurements obtained by solvent extraction. The subsequent in situ characterization of organic compounds through micro-Raman spectroscopy indicates the same biogeochemical signatures of the microbialites within the cryptic cavities of the biostalactites of modern marine caves as those inside the skeletal framework of Carnian patch reefs. These data, showing the same processes in Triassic and modern cryptic microenvironments, is evidence that the microbially mediated precipitation in confined environments is a process independent of geological time that further investigation may be able to test.
The distribution of macroinfauna and Total Organic Carbon (TOC) were investigated in the muddy substrates along a transect at 14 m depth in the Grotta Azzurra (Capo Palinuro, Tyrrhenian Sea, Italy), a submarine cave with warm (18-24degreesC) sulphur-water springs in its innermost, aphotic chamber. Due to thermal stratification, sulphidic compounds remain trapped above the cooler sea-water in the anoxic upper sulphidic layer supporting dense sulphur-oxidizing bacterial mats that detach and disperse when disturbed. The macroinfauna of Grotta Azzurra comprised 97 species. The assemblage bore similarities to those previously described from non-cave Mediterranean oligotrophic regions, and also indicated environmental instability. Unlike in other caves, where benthic zonation is prominent, no inward decrease of macroinfaunal abundance or diversity was observed. It is assumed that the chemosynthetic inputs in the inner region provide an additional source of food that has a positive effect on the colonization and survival of macroinfauna inside the resource limited cave environment.
Over the last fifteen years, sulphidic karst has received increasing recognition as unique systems where new discoveries of both biological and geological features have captured the imagination of the public media and the academic community. The unique resources found within both active and relict sulphidic karst systems are globally important to karst conservation issues. In this paper we describe some of the unique geological and biological features of sulphidic caves and karst and present strategies for the conservation and protection of this exceptional habitat.
Submarine caves, cavities and niches characterised by H2S elevated concentrations are particularly interesting for their inhabiting microflora as well as for the overall chemical, geological and biological parameters. These ecosystems are usually populated by well adapted living forms, physically distributed following the in situ concentration and gradient of micronutrients, O2 and H2S, and also according to the values of temperature and pH. The biota is primarily characterised by prokaryotes (both autotrophic and heterotrophic) adapted to anoxic and/or microaerophilic condition and capable to form extensive biofilms on the rocky surfaces and even on the bottom sediment. These habitats can be defined as extreme, because the scarcity or absence of solar irradiation, the chemo-physical traits and the fact that specialised prokaryotes are often the only inhabitants. This review is focused on the microbial ecology of marine caves and holes characterised by high levels of hydrogen sulphide. Ecological and geological data are already available but very few insights as far as regard microbiology were achieved in order to describe these fascinating habitats. The autochthonous mesophilic and thermotolerant microorganisms living in these caves may have interesting physiological traits and eventually may lead to potential application in biotechnological processes.
Black holes are vertical cave systems, which have no known lateral passages and form in the interior stable regions of the larger Bahamian islands. They are found where the land is transitional between submerged and dry land, not dissimilar to saltmarsh environments. Most Black Holes are located in the central to western side of the island of South Andros in the Bahamas, although one has been found on the northern transitional shore of Grand Bahama Island. The water in these holes appears black in colour due to the presence of a 1 m thick microbial layer located within the upper third of the water column (18–19 m) at the boundary between the oxic low salinity upper water mass and the denser anoxic saline water layer. The boundary between the two water masses is characterised by sharp discontinuities in physico-chemical gradients: salinity increased from 12 to 35 psu; temperature from 29°C to 36°C; pH decreased from pH 8.6 to 6.45 and dissolved O2 from 6 mg/l to <1 mg/l. Anoxygenic phototrophic bacteria belonging to the genera Allochromatium and Thiocapsa have been identified as the dominant members of this warm (36°C), saline, sulphide rich layer and achieve population densities >107 viable cells/ml. Calculations reveal that this layer of anoxygenic phototrophic bacteria, in the South Andros Black Hole may have a biomass content of approximately 5.06 ton dry weight.
Modern microbial mats and microbialites are described from basaltic sea caves on the island of Kauai, HI. The mats grow on the ceilings and walls in the photic zone of several open caves where fresh water seeps out of the rock. Scanning (SEM) and transmission electron microscopy (TEM) showed that the active mats are dominated by filamentous and nonfilamentous cyanobacteria in the surface layers and heterotrophic bacteria in deeper layers. Energy dispersive X-ray analysis revealed that copious amounts of extracellular polymeric substances (EPS) are rich in Mg, Si, O, and Ca, likely concentrated from solution. Petrographic microscopy and electron microprobe analysis of the mineralized microbialites showed textures reminiscent of stromatolitic laminations, consisting mainly of alternating calcium carbonate (calcite and aragonite) and magnesium-rich silicate (kerolite). Thin coatings rich in magnesite, hydromagnesite and monohydrocalcite surround the microbialites on the rock surfaces and are likely inorganic in origin. Within the mats, minerals tend to form and concentrate within, or around, dense matrices of EPS. Microenvironments with geochemical conditions favorable for mineral crystallization likely develop in the mats as a result of the mucilaginous extracellular material and the development of bacterial microcolonies. In addition, copious amounts of extracellular polymers bind ions from solution and provide nucleation sites for mineral crystallization and growth. This combination of biological and inorganic processes can explain the occurrence of the secondary minerals in these caves, as well as the stromatolitic textures of the microbialites.
Waste of electric–electronic equipment (WEEE) with an annual growth rate of about 3–5% is the fastest growing waste stream in municipal wastes. Notwithstanding their environmental pollution potential, waste of electrical and electronic equipment (WEEE) with their high content of base and precious metals, in particular, are regarded as a potential secondary resource when compared with ores. For the recovery of metals from WEEE, various treatment options based on conventional physical, hydrometallurgical and pyrometallurgical processes are available. These process options with particular reference to hydromet-allurgical processes were reviewed in this study. With their relatively low capital cost, reduced environmental impact (e.g. no hazardous gases/dusts), potential for high metal recoveries and suitability for small scale applications, hydrometallurgical processes are promising options for the treatment of WEEE. Since the metals are present in native form and/or as alloys, an oxidative leaching process is required for the effective extraction of base and precious metals of interest. A two-stage process based on oxidative acid leaching of base metals (Cu in particular) followed by leaching of precious metals using cyanide, thiosulfate, thiourea or halide as lixiviant(s) can be suitably developed for the hydrometallurgical treatment of WEEE. However, further research is required to develop new, cost effective and environmentally friendly processes and/or refine existing ones for leaching and, in particular, downstream processes.
Microbial mats from hydrogen suléde-rich waters and cave-wall bioélms were inves- tigated from Cesspool Cave, Virginia, to determine community composition and po- tential geomicrobiological functioning of acid-producing bacteria. Rates of microbial mat chemoautotrophic productivity were estimated using (14C)-bicarbonate incorpo- rations and microbial heterotrophy was determined using (14C)-leucine incubations. Chemoautotrophic éxation wasmeasured at30.4 §12.0 ngCmg dry wt¡1h¡1, whereas heterotrophic productivity was signiécantly less at 0.17 § 0.02 ng C mg dry wt¡1h¡1. The carbon to nitrogen ratios of the microbial mats averaged 13.5, indicating that the mats are not a high quality food source for higher trophic levels. Ribosomal RNA-based methods were used to examine bacterial diversity in the microbial mats, revealing the presence of at least éve strains of bacteria. The identity of some of the strains could be resolved tothe genus Thiothrix and the Flexibacter-Cytophaga-Bacteriodes phylum, and the identity of the remaining strains was to either the Helicobacter or Thiovulum group. Two of 10 sulfur-oxidizing, chemoautotrophic pure cultures of Thiobacillus spp. (syn.Thiomonas gen. nov.)demonstrated the ability tocorrode calcium carbonate, sug- gesting that the colonization and metabolic activity of these bacteria may be enhancing cave enlargement.
Modern and fossil chemosynthetic communities based on the consumption of gases (carbon dioxide, methane, hydrogen sulfide, and others) are widespread on the Earth surface, where they have produced geologic bodies distributed over a wide time slice. These communities are entirely sustained by gas-bearing cold fluids, coming to the surface from the upper crust, around which they grow. This kind of outgassing is not linked to volcanic activity and there is not hydrothermal influence. Cold outgassing is probably present on Mars, it has been observed on Ganymede, Europa, and other icy satellites (ice volcanism), and is theoretically considered to be present on Titan. This possible extensive occurrence of outgassing sites on the planetary surface suggests that chemosynthesis may be an important player in the biology of the Solar System.
Hydrothermal vent ecosystems have been extensively investigated during the last 20 years; shallow water hot springs (typically found below 50 m depth) have also been studied, and from these ecosystems many thermophilic and hyperthermophilic organisms were isolated and described.
The submarine caves of Cape Palinuro were discovered long ago, but only during the last decades were geological and biological investigations carried out, yielding a large number of reports on this fascinating environment. During the last two years, several samples of water, mud, and/or bacterial mat were collected within the “Grotta Azzurra”, and enrichment experiments were performed using peptone, starch, glucose or pullulan as main organic nutrients. Many heterotrophic strains were isolated and most of them grew optimally between 37 and 43 ° C with the addition of 0-2 % NaCl. Growth was usually observed between 10 and 50 ° C the range of growth pH was 4 to 9, and NaCl concentrations up to 10–12 % were tolerated in most cases.
The analysis of 16S rDNA performed with the most representative isolates showed a close phylogenetic relationship with the genera Bacillus, Vibrio, Citrobacter and Escherichia. Moreover, an isolate showing morphological and physiological similarities with the genus Enterococcus was characterised and taxonomically described based on the 16S rDNA sequence.
The demand for metals is ever increasing with the advancement of the industrialized world. On the other hand, worldwide reserves of high grade ores are close to depletion. However, there exists a large reserve of metals in low and lean grade ores and other secondary sources. Metal recovery from low and lean grade ores using conventional techniques such as pyrometallurgy, etc. requires high energy and capital inputs which often result in the secondary environmental pollution. Thus, there is a need to utilize more efficient technologies to recover metals. Biohydrometallurgy, which exploits microbiological processes to recover metal ions, is regarded as one of the most promising and revolutionary biotechnologies. The products of such processes are dissolved in aqueous solution , thereby rendering them more amenable to containment, treatment and recovery. On top of this, biohy-drometallurgy can be conducted under mild conditions, usually without the use of any toxic chemicals. Consequently, the application of biohydrometallurgy in the recovery of metals from lean grade ores and wastes has made it an eco-friendly technology for enhanced metal production. This paper reviews the current status of biohydrometallurgy of low grade ores around the world. Particular attention is focused on the bioleaching of black shale ore and its metallogenic diversity in the world. The review assesses the status of bioprocesssing of metals to evaluate promising developments. Bioleaching of metals is comprehensively reviewed with the emphasis on the contribution of microbial community, especially fungal bioleaching coupled with ultrasound treatment. In this manuscript, the principles of bioleaching, their mechanisms, and commercial applications are presented. The case studies and future technology directions are also reviewed.
The first laboratory tests on biooxidation and cyanidation of gold ores in Turkey were carried out using samples of the Copler Gold Mine. Over a 3 year R&D test period, mixed bacterial/archaeal cultures improved biooxidation of the Copler ore. The highest sulphide oxidation of 87.35% over 432 h was achieved in shake flasks in the presence of the mixed culture (MODM: Sulfolobus acidophilus and Sulfolobus thermosulfidooxidans). Bioreactor tests resulted in greater dissolution rates for iron and arsenic than did shake-flask tests, which led to a greater extent of sulphide oxidation within a shorter period of time. The maximum sulphide oxidation in the bioreactor tests was 97.79% after 240 h when the EXTM (Acidianus brierleyi and Sulfolobus metallicus) mixed culture was used. After the biooxidation experiments with solids contents of 10% and 20% (w/v), the gold recovery from the oxidised ore was lower than that achieved in the presence of 5% solids (w/v) because the extent of sulphide oxidation was reduced as the pulp density increased. A strong correlation between the sulphide oxidation and gold recovery was also established. The highest gold recovery of 94.48% was achieved during cyanidation from the biooxidised ore produced from the experiment conducted using the EXTM mixed culture.
The geo-biological exploration of a pockmark field located at ca. −800m in the Gela basin (Strait of Sicily, Central Mediterranean) provided a relatively diverse chemosymbiotic community and methane-imprinted carbonates. To date, this is the first occurrence of such type of specialized deep-water cold-seep communities recorded from this key region, before documented in the Mediterranean as rather disjunct findings in its eastern and westernmost basins. The thiotrophic chemosymbiotic organisms recovered from this area include empty tubes of the vestimentiferan Lamellibrachia sp., loose and articulated shells of lucinids (Lucinoma kazani, Myrtea amorpha), vesicomyids (Isorropodon perplexum), and gastropods (Taranis moerchi). A callianassid decapod (Calliax sp.) was consistently found alive in large numbers in the pockmark mud. Their post-mortem calcified parts mixed with molluscs and subordinately miliolid foraminifers form a distinct type of skeletal assemblage (named DECAMOL). Carbonate concretions display �13C values as low as −40‰ PDB suggesting the occurrence of light hydrocarbons in the seeping fluids. Since none of the truly chemosymbiotic organisms was found alive, although their skeletal parts appear at times very fresh, some specimens have been AMS-14C dated to shed light on the historical evolution of this site. Lamellibrachia and Lucinoma are two of the most significant chemosymbiotic taxa reported from various Mediterranean cold seep sites (Alboran Sea and Eastern basin). Specimens from station MEDCOR78 (pockmark#1, Lat 36�46010.1800 N, Long 14�01031.5900 E, −815 m) provided ages of 11 736±636 yr cal BP (Lamellibrachia sp.), and 9609.5±153.5 yr cal BP (L. kazani). One shell of M. amorpha in core MEDCOR81 (pockmark#6, Lat 36�45038.8900 N, Long 14�00007.5800 E, −822 m) provided a
sub-modern age of 484±54 yr cal BP. These ages document that fluid seepage at this 25 pockmark site has been episodically sustaining thiotrophic macrobenthic communities since the end of the Younger Dryas stadial up to sub-recent times.
The Microbial hydrometallurgy and microbial mineral processing of metal sulphides is currently a well established
technology. Over past years there has been a huge amount of developments with regards to the understanding of its both
engineering perspective as well as fundamental approach with regards to the microorganisms. The huge diversity of the
microorganisms, which has come into picture over the years of research and development have made the engineers to go
beyond several limitations of working temperature to salt tolerance of the microorganisms in harsh conditions to deliver
better technologies for the future operative plants. Today scientists have been able to deliver the various mechanisms
involved in bioleaching but still there are facets to be really understood and more importantly on the front how lab scale
research can be turned out into full scale operation by scaling up the research and optimizing the engineering aspects of the
research. Most of the bioleaching operation has shown their productivity in commercial application of refractory gold
concentrates using mesophilic microorganisms followed by the cyanide leaching to recover optimum amount of gold with an
environment friendly method compared to the conventional method of roasting. Research in the area of chalcopyrite
bioleaching is still continuing o solve the mysteries of jarosite precipitation and formation of passivation layer, which
inhibits the copper recovery in a heap leaching of chalcopyrite by biological methods. Use of extreme thermophiles in
chalcopyrite bioleaching is making a revolutionary movement to solve the mystery behind the scaling up the process, which
could be possible to be solved in future. Bioleaching with other sulphide minerals together with Acid Mine Drainage (AMD)
mitigation, which is a serious concern today, is taking is taking shape today in order to cater the needs of the mankind.
However the biohydrometallurgy research seems to contribute to a greater extent in framing environmental friendly process
with regards to hydrometallurgical operations in future and establish a developed technology to benefit human beings needs
by its upcoming research and development.
Keywords: Biomining, refractory gold, copper, chalcopyrite, bioleaching, nickel sulphide, biooxidation, acid mine drainage
The diversity of bacteria and archaea was characterized from sediments collected from Wind Cave located in Wind Cave National Park in the Black Hills of South Dakota. Wind Cave is a limestone dissolution cave with strata that started forming over 300 million years ago, making it one of the oldest in the world. Previous work suggested that the cave was largely a detritus based system ultimately dependent upon allochthonous energy and carbon from photosynthesis of the overlying vegetation, and algae growing near lights along the tour routes. In this work, we used a molecular phylogenetic approach to characterize the microbial structure and infer a corresponding ecosystem function where appropriate. Four bacterial divisions and subdivisions were found in the culture collection, which represented 14 phylotypes, whereas 12 divisions and subdivisions were identified in the clonal analysis comprising 49 phylotypes. The predominant groups were the gamma-Proteobacteria and Acidobacteria. Although a few of the clones resembled sequences from other cave and subterranean systems, no cave-specific bacterial community was evident in this work. Archaeal phylotypes (20 Crenarchaeota and 2 Euryarchaeota) were detected, with a large proportion of the Crenarchaeota resembling sequences from a South African gold mine. One archaeal cluster in particular appears to be specific to the subterranean environment. Most of the microbial sequences were not related to known chemolithoautotrophs, therefore we conclude that this particular community is likely detritus based where allochthonous energy and carbon are transported into the cave by infiltrating waters.
Sampling Air-Filled Caves
Like all members of the genus Thioploca, two new marine thioplocas from the benthos of the Chilean continental shelf were found to be colonial, multicellular, gliding trichomes of uniform diameter enclosed by a common sheath. However, the cellular sulfur inclusions were located in the thin peripheral cytoplasm surrounding a large, central vacuole. Gliding motility of these organisms did not persist in diluted seawater, under fully aerobic conditions, or in anaerobic atmospheres. Low concentrations of sulfide (100 μM) were beneficial. The trichome diameters of Thioploca araucae ranged from 30 to 43 μm, and those of Thioploca chileae ranged from 12 to 20 μm. Neither species has been isolated in pure culture.
The ultrastructure of Beggiatoa alba strain B15LD was examined in detail using thin section and freeze-etch techniques. The cell wall complex consisted of five discrete layers external to the cytoplasmic membrane. The surface layer was the most distinct, containing linearly arranged longitudinal fibrils, 10-12 nm in diameter. Sulphur inclusions observed in thin sections had a 12-14 nm thick pentalaminar envelope and were external to the cytoplasmic membrane. Similar pentalaminar envelope structures were observed in cells grown without hydrogen sulphide, but they were small, folded and probably lacked sulphur. After a few hours of exposure to hydrogen sulphide, large sulphur inclusions were present in the cells, presumably due to the expansion of the folded ‘rudimentary’ vesicles to accommodate the deposited sulphur. The location and morphology of the cytoplasmic membrane invaginations which surrounded the sulphur inclusions were elucidated by thin sectioning and freezeetching. A three-dimensional model of the cell envelope structure is presented.
The gills of Myrtea spinifera carry large numbers of Gram-negative bacteria within the
epithelia1 cells of the subfilamentar region and contain elemental sulphur. Haemoglobin which has a
high affinity for oxygen is present in the gill tissue. Homogenates of gill tissue fix carbon dioxide vJa
ribulosebisphosphate carboxylase and contain 3 enzymes concerned in the oxidation of sulphur,
adenylylsulphate reductase, sulphate adenylyltransferase and sulphate adenylyltransferase (ADP).
Fixation of carbon dioxlde by whole gills is enhanced by free sulphide. Whole gills accumulate
labelled sulphur when supplied with Na235S, and a major proportion of the labelled sulphur is
metabolized to non-volatile compounds or is bound to the tissues. The bacteria are evidently
chemoautotrophs and presumably obtain energy for fixation of carbon dioxide by oxidation of reduced
sulphur compounds. The haemoglobin is not apparently involved in transport of sulphide but may
control oxygen tension close to the bacteria. The sediment in which the bivalves live is low in sulphide
compared with some coastal muds and the hydrothermal vents. The interstitial water contains less than
1 pM of dissolved sulphide and the sediment releases less than 700 pmoles dm-3 of dissolved sulphide
when treated with dilute acid. Habitats with similar low concentrations of dissolved sulphide are
widespread in nature. An ability to exploit such low levels of reduced sulphur must be nlutually
advantageous to host and bacteria, though as yet we have no direct evidence for transfer of organic
matter from bacteria to host. To obtain sufficient energy for growth and maintenance of the association,
the bacteria must have access to the sediment-bound sulphide.
MARINE species of Thioploca occur over 3,000 km along the continental shelf off Southern Peru and North and Central Chile(1-4). These filamentous bacteria live in bundles surrounded by a common sheath and form thick mats on the sea floor under the oxygen-minimum zone in the upwelling region, at between 40 and 280 m water depth. The metabolism of this marine bacterium(5,6) remained a mystery until long after its discovery(1,7). We report here that Thioploca cells are able to concentrate nitrate to up to 500 mM in a liquid vacuole that occupies >80% of the cell volume. Gliding filaments transport this nitrate 5-10 cm down into the sediment and reduce it, with concomitant oxidation of hydrogen sulphide, thereby coupling the nitrogen and sulphur cycles in the sediment.
Ten sediment trap arrays were deployed over two years for periods of 3 to 40 days in three different sampling points along a 50 m long Mediterranean submarine cave. Mean total particulate matter flux decreased strongly from the semi-dark area (3.3 g m-2 d-1) to the dark area (0.8 and 0.6 g m-2 d-1). Carbon represented 3.3% to 3.5% and nitrogen 0.34% to 0.38% of settling dry matter. The decrease in organic input from the entrance to the terminal part of the cave results in increasingly oligotrophic conditions with distance from the cave entrance. Horizontal resource limitation can be connected with a strong zonal decrease in fauna richness. Biomass declines both in hard substrate and soft bottom communities. Despite major differences, some similarities are noticed between oligotrophic conditions that may occur in the dark cave and those in around 1000 m depth ecosystems. Dark oligotrophic submarine caves can be considered to be good scale models for the study of some aspects of general trophic pathways.
An accurate most-probable-number enumeration method was developed for counting the number of Beggiatoa trichomes from various freshwater sediments. The medium consisted of extracted hay, diluted soil extract, 0.05% acetate, and 15 to 35 U of catalase per ml. The same enrichment medium, but without the acetate, was the best enrichment medium from which to obtain pure cultures because it supported good growth of the beggiatoas without allowing them to be overgrown by other bacteria. A total of 32 strains of Beggiatoa were isolated from seven different freshwater habitats and partially characterized. The strains were separated into five groups based on several preliminary characteristics. Four of the groups contained cells with trichomes of approximately the same diameter (1.5 to 2.7 mum) and may be Beggiatoa leptomitiformis or an unnamed species. The fifth group appeared to be Beggiatoa alba. With the exception of three strains, all of the strains deposited sulfur in the presence of hydrogen sulfide, and all strains grew heterotrophically and deposited poly-beta-hydroxybutyrate and volutin when grown on acetate supplemented with low concentrations of other organic nutrients. Thin sections of sulfur-bearing trichomes indicated that the sulfur granules were external to the cytoplasmic membrane and that they were surrounded by an additional membrane.
The interactions between colorless sulfur bacteria and the chemical microgradients at the oxygen-sulfide interface were studied in Beggiatoa mats from marine sediments and in Thiovulum veils developing above the sediments. The gradients of O(2), H(2)S, and pH were measured by microelectrodes at depth increments of 50 mum. An unstirred boundary layer in the water surrounding the mats and veils prevented microturbulent or convective mixing of O(2) and H(2)S. The two substrates reached the bacteria only by molecular diffusion through the boundary layer. The bacteria lived as microaerophiles or anaerobes even under stirred, oxic water. Oxygen and sulfide zones overlapped by 50 mum in the bacterial layers. Both compounds had concentrations in the range of 0 to 10 mumol liter and residence times of 0.1 to 0.6 s in the overlapping zone. The sulfide oxidation was purely biological. Diffusion calculations showed that formation of mats on solid substrates or of veils in the water represented optimal strategies for the bacteria to achieve a stable microenvironment, a high substrate supply, and an efficient competition with chemical sulfide oxidation. The continuous gliding movement of Beggiatoa cells in mats or the flickering motion of Thiovulum cells in veils were important for the availability of both O(2) and H(2)S for the individual bacteria.
Microbial communities in marine hydrothermal sediments (0 to 30 cm deep) in an inlet of Kodakara-Jima Island, Kagoshima, Japan, were studied with reference to environmental factors, especially the presence of amino acids. The study area was shallow, and the sea floor was covered with sand through which hot volcanic gas bubbled and geothermally heated water seeped out. The total bacterial density increased with depth in the sediments in parallel with a rise in the ambient temperature (80(deg)C at the surface and 104(deg)C at a depth of 30 cm in the sediments). As estimated by most-probable-number studies, hyperthermophilic sulfur-dependent heterotrophs growing at 90(deg)C dominated the microbial community (3 x 10(sup7) cells (middot) g of sediment(sup-1) at a depth of 30 cm in the sediments), followed in abundance by hyperthermophilic sulfur-dependent facultative autotrophs (3.3 x 10(sup2) cells (middot) g of sediment(sup-1)). The cooler sandy or rocky floor surrounding the hot spots was covered with white bacterial mats which consisted of large Beggiatoa-like filaments. Both the total organic carbon content, most of which was particulate (75% in the surface sediments), and the amino acid concentration in void seawater in the sediments decreased with depth. Amino acids, both hydrolyzable and free, constituted approximately 23% of the dissolved organic carbon in the surface sediments. These results indicate that a lower amino acid concentration is probably due to consumption by dense populations of hyperthermophilic sulfur-dependent heterotrophs, which require amino acids for their growth and thus create a gradient of amino acid concentration in the sediments. The role of primary producers, which supply essential amino acids to sustain this microbial community, is also discussed.
Some filaments are like those described from the deep hydrothermal vents, except their biggest size. Indeed, the largest filaments, 76-100 μm, resemble Beggiatoa but they are not fixed on a substratum. The bacterial strains isolated from this site are mixotrophic, and grow on thiosulfate as well as on organic compounds. -from English summary
The primary production of organic carbon by chemosynthetic sulfur-oxidizing bacteria has been proposed to provide the base of the food chain for the extensive populations of animals found at hydrothermal vents at depths of about 2600 m. The oxidation of reduced inorganic compounds (such as H2S, S0, S2O
32−, NH
4+, NO
22−, Fe2+ and possibly Mn2+) as the source of energy for chemosynthesis is equivalent to the role of light in photosynthesis. Reported here is the present state of proof of this hypothesis which includes the work of many collaborating scientists. Epifluorescence microscopy and nucleotide determinations demonstrated substantial bacterial densities in the emitted vent waters. Multi-layered mats of unicellular bacteria were observed, often encased in heavy Mn/Fe deposits, as well as assemblages of Leucothrix/Thiothrix-like filaments and others resembling trichomes of apochlorotic cyanobacteria. Masses of Beggiatoa filaments were found on artificial surfaces deposited near the vents for 10 months. Species of the genera Thiomicrospira, Thiobacillus and Hyphomonas have been isolated and studied in detail. Furthermore, an anaerobically chemosynthetic, extremely thermophilic, methanogenic bacterium was isolated as well as a number of “Type I” methylotrophic bacteria oxidizing methane and methylamine. The gills of bivalves, collected from areas intermittently flushed with H2S-containing vent water and oxygenated ambient seawater, contained masses of bacteria showing high activities of sulfur metabolism and Calvin-Benson cycle enzymes. Likewise the “trophosome” tissue of the gutless tube worm Riftia was found to consist of procaryotic cells exhibiting ATP-generating and CO2-reducing activity. Thus, three locations of chemosynthetic production are proposed: (1) within the subsurface vent system at elevated temperatures, (2) in microbial mats in the immediate surrounding of the vents, and (3) in various symbiotic associations with invertebrates. It appears that the predominant chemosynthetic production, in combination with the most efficient transfer of organic carbon to the vent animals, occurs via symbiosis.
A morphological study of bacteria associated with the "Pompei worm,"Alvinella pompejana, collected from East Pacific rise hydrothermal vents, revealed four types of epidermal associations on the dorsal part of the animals: various single cells distributed on the animal tegument; clump-like associations located in the intertegumentary spaces; and filamentous bacteria associated with epidermal expansions, or inserted on the posterior parapodia. The bacterial morphologies were illustrated by SEM and TEM pictures and compared to bacteria previously described. The functional significance of these associations is discussed.
In the hypersaline lagoon at Laguna Figueroa vertically stratified diverse communities of microorganisms thrive. The modern sediments of Baja California at Laguna Figueroa contain cyanobacterial communities and sedimentary structures produced by these blue greens that have already been studied by Horodyski and his colleagues. This paper provides an introduction to the complex microbial communities, primarily those that underlie the laminated Microcoleus mats. They are composed of anaerobic photosynthetic and heterotrophic bacteria.
1.
An der Mündung einer Schwefelquelle im Hafen von Split (Adriatisches Meer, Jugoslavien) wurde ein reiches Beggiatoenlager entdeckt. Zwischen anderen, mehr oder weniger allgemein verbreiteten Arten (Beggiatca allca, B. leptcmitiformis, B. arachnoidea) befanden sich auch reichliche Lager von zwei verschieden breiten Formen einer größeren Beggiatoa, die nach dem bestehenden System zu der damit für das Adriatische Meer und Jugoslavien zuerst nachgewiesenen B. mirabilis Cohn gestellt werden mußten.
2.
Durch variationsstatische Verarbeitung des Materials ließ sich zeigen, daß in ihm zwei durch die Breite der Fäden sowie durch das Verhältnis der Zellenhöhe zu Zellenbreite zu unterscheidende, übergangslose Formen enthalten sind, deren systematische Trennung notwendig erschien. Beide Formen wurden als Arten aufgestellt. Die schmälere Form (14,8 bis 21,4 μ) wurde als B. mirabilis (Cohn) Klas, die breitere Form (26,4 bis 42,8 μ) dagegen als B. gigantea Klas bezeichnet.
3.
Auf Grund eingehender systemtischer Analyse und unter Berücksichtigung aller älteren Angaben ist meiner Ansicht nach diese Trennung auch auf alle 15 bis 45 bzw. 55 μ breiten, bisher unrichtigerweise als B. mirabilis Cohn benannte Beggiatoenformen anzuwenden, wobei dann natürlich der obere Breitengrenzwert der B. gigantea mit 55 μ zu fassen wäre.
FILAMENTOUS sulphide-oxidizing bacteria, Beggiatoa spp., com-monly grow as submillimetre-thin white films on anoxic marine sediments. Unusually thick mats (>1 cm) of giant Beggiatoa filaments, 41–120 μm wide and 2–10 mm long, were observed at 2,000 m water depth in the hydrothermal vent fields of Guaymas Basin, Gulf of California1–4. We investigated how such dense communities of the largest known bacteria overcome severe diffusion limitation of their substrate supply, and what advantage they may have by developing such large cell sizes. Oxygen, sulphide, pH and temperature were therefore measured in Beggiatoa mats directly on the sea floor. We report here the discovery of small-scale hydrothermal fluid circulations around patches of the bacteria, causing a pulsatory seawater flow into the mats and thereby enhancing the supply of oxygen and sulphide to the bacteria.
Submarine caves with sulphurous springs at Cape Palinuro, Campania, Italy, have a richer fauna than expected from the known oligotrophic nature of the cave habitat. Warm water containing sulphide issues from springs and rises above the cooler ambient seawater with a sharp thermocline/chemocline between. The warm water then escapes from the caves mixed with cooler sea- water, probably inducing an inflow of ambient sea-water. Bacterial mats, often dominated by large species of attached bacteria resembling Beggiatoa, line the upper parts of the inner caves and act as primary producers, fixing CO2 by means of the autotrophic enzyme ribulosebisphosphate carboxylase. Many of the animals in the innermost parts of the caves live close to the chemocline or just below, where they would experience fall-out of bacterial organic matter, and some carry filamentous bacteria on their tubes and hard parts. Dominant members of the community include sponges, cnidarians, and tubicolous polychaetes. The inner caves form a two compartment system, with production in the upper layer of sulphurous water and consumption below. The carbon isotope ratio in the bacterial mats (range of δ13C-30.1 to-31.8‰) is a good 'marker' for tracing carbon flow, contrasting with the usual enhancement of carbon-13 in benthic photoautotrophs. Animal tissue isotope ratios confirm that bacterial carbon is entering the food chain and that this is a source of food for some cave biota. The contribution from bacteria ranges from zero to virtually 100%, depending on species and variation in local habitat. Animals living close to the bacterial mats benefit most, notably a polychaete Phyllochaetopterus, an oligochaete Thalassodrilides, a podocopid ostracod Paracypris and certain echinoderms and bivalves. The large sponges (Geodia, Petrosia) may not benefit from bacterial production.
A marine ecosystem in the crater of the Ushishir Volcano (Kraternaya Bight, Yankich Island, the Kuriles) showing gasothcrmal activity was studied for hydrographical, hydrochemical, and biological characteristics. Maximal changes in chemical and biological characteristics were observed in the surface water layer of 0–5 m. This layer had higher water temperature, was saturated with volcanogcnic carbon dioxide (up to 2000 10-6 torr), ovcrsaturatcd with oxygen (up to 200 %), and contained high concentrations of chlorophyll a. Hydrogen sulfide was found in the surface water layer and at a depth of 15 m in the area of maximal effect of volcanic effluents.
The planktonic community is characterized by high rates of production and destruction of organic matter only in the 0–5 m layer. Daily vertical migrations of the ciliatc Mesodinium rubrum were observed, which caused “red tides”.
Bacterial, algobacterial, and diatom mats developed on the bottom of the bight in the zone of gasohydrothermal vents and in areas of volcanic water seeping. The rate of organic matter production in algobacterial mats reached 33.4g C-rrr2-d-l, chcmolithotrophy predominating. Bottom settlements had high population density and great animal biomass, which reached 10 kg m-2 in gasohydrothermal fields. They obtain sufficient energy from primary production of microphy-tobenthos, algobacterial, and bacterial mats. Bcnthic species dominant in the bight were not found off the Ushishir Islands.
Some species of macrobenthos inhabiting the Kraternaya Bight differ markedly in size and biomass from the same species found beyond the bight.
A new type of animal community has been found near hot vents in the subpolar Atlantic at 100 to 106 m depth off Kolbeinsey on the Jan-Mayen ridge. Incubation of high temperature fluids yielded cultures of undescribed hyperthermophilic eu- and archaebacteria, growing in a temperature range between 70 and 110C depending on the isolates. Bacteria are closely related to species occurring within deep sea hydrothermal areas. In contrast to deep-sea vent sites of the Mid-Atlantic and other oceans, the Kolbeinsey macro- and meiofauna consists of species reported from non-vent areas in the boreal Atlantic and adjacent polar seas. The most abundant forms are a solitary hydroid polyp and two sponges. Kolbeinsey is an isolated and young area of hydrothermal activity at relatively low depth and in highly productive waters; these findings could indicate a model for an early evolutionary step towards the formation of a genuine specialized vent community.
The populations of Beggiatoa species were quantified in the sediments of a brackish fjord (Limfjorden, Denmark) over a period of 1 year. The bacterial distribution was compared to the physical structure of the sediment, the redox profile, the concentration and production rate of H2S, and the rate of O2 consumption. The bacteria are absent in fine and in medium-grained sand, but in muds which are aggregated in faecal pellets very high population densities are found throughout the year with average biomasses of 5 to 20 g m-2. The bacteria seldom form coatings on the surface, but are distributed within the upper few centimeters of oxic sediment. They receive H2S partly from the lower anoxic layers and partly from reduced microniches scattered in the oxidized zone. Estimates of their metabolic rates indicate that Beggiatoa spp. may play a significant role in the sulfur and carbon cycles of the investigated sediments.
Microscopic examination of the whitish mat that covered the substrata around subtidal hydrothermal vents at White Point in southern California revealed a Thiothrix-like bacterium containing sulfur inclusions as the dominant filamentous form in this microbial community. The matlike appearance developed as a result of the closely-packed manner inwhich the basal ends of the filaments were anchored to the substrate. The dominant phospholipid fatty acids of these filaments (16:0, 16:1w7c, 18:0, 18:1w7c) were similar to those recovered from a sample of Beggiatoa isolated from a spring in Florida. Filaments from both sources contained small quantities of C18 and C20 polyunsaturated fatty acids, as well. A larger but less abundant sheathless, filamentous form, which also contained sulfur inclusions and displayed a cell wall structure similar to a previously described Thioploca strain, also colonized the substrata around the subtidal mat. The preservation methods used in the preparation of thin-sections of the subtidal mat material were found to be inadequate for defining some key cellular structures of the large filaments. Nevertheless, the results demonstrate that the filamentous bacteria comprising the microbial mat in the vicinity of the subtidal vents exhibit some of the features of the free-living filamentous microorganisms found in deep-water hydrothermal areas.
A community of abundant suspension-feeding organisms was photographed around an active hydrothermal vent at the Galapagos Rift. A site on the crest of the East Pacific Rise where hydrothermal discharge is suspected also has a dense colony of sessile organisms. The high standing crop of macrobenthos in these patches probably results from local increases of deep-sea food supply near hydrothermal plumes in the bottom water.
Microbial mats characteristically are dominated by a few functional groups of microbes: cyanobacteria, colorless sulfur bacteria, purple sulfur bacteria, and sulfate-reducing bacteria. Their combined metabolic activities result in steep environmental microgradients, particularly of oxygen and sulfide.The driving force of most microbial mats is photosynthesis by cyanobacteria and algae. Subsequently, sulfate-reducing bacteria, using excretion-, lysis-, and decomposition products of cyanobacteria, produce sulfide by the dissimilatory reduction of sulfate. The sulfide can be reoxidized to sulfate by colorless and purple sulfur bacteria.Colorless sulfur bacteria are chemotrophic organisms primarily oxidizing sulfide and other reduced forms of sulfur with oxygen to obtain energy. The oxidation of reduced sulfur species also provides reducing equivalents for the reduction of carbon dioxide to cellular carbon. The final product of sulfide oxidation is sulfate, with elemental sulfur, deposited extracellularly, as the principal intermediate.Purple sulfur bacteria primarily are anaerobic phototrophic organisms using sulfide and other reduced forms of sulfur exclusively as the electron donor for the reduction of CO2 to cellular carbon. Usually, sulfur is temporarily stored intracellularly. The final product of the oxidation of reduced forms of sulfur is sulfate.The niches for these metabolically different groups of microbes in ecosystems with steep, often non-overlapping, gradients of oxygen and sulfide appear to be spatially separated. However, maximum viable counts of colorless sulfur bacteria and purple sulfur bacteria were both found in the top 5–10 mm of mats. Unexpectedly, viable counts of sulfate-reducing bacteria also peaked at the same depth horizon.Sulfide is inhibitory for most oxygenic phototrophs. Sulfide production immediately underneath the layer of cyanobacteria might inhibit their growth, and, consequently, that of the entire ecosystem. In microbial mats this effect is minimized by the combined action of colorless and purple sulfur bacteria. Colorless sulfur bacteria generally have a much higher affinity for sulfide than purple sulfur bacteria, however, in microbial mats, their activity is hampered by low oxygen supply rates. As shown by pure culture studies with colorless sulfur bacteria, sulfide is incompletely oxidized when oxygen is short in supply, resulting in the production of potential electron donors for purple sulfur bacteria, such as sulfur, thiosulfate and polysulfides. In the absence of purple sulfur bacteria, colorless sulfur bacteria would not be able to maintain a low sulfide concentration due to shortage of oxygen, which in turn would result in increased inhibition of oxygenic photosynthesis.It thus appears that the combined action of all four groups of functional microbes mentioned effectively results in optimal growth of these recent “stromatolites”.
Subtidal springs in and around the submarine limestone cavern of Grotta Azzurra, at Capo Palinuro, Italy, discharge fluids which are warm (< 25°C), mildly acidic, depleted in Cl−, Na+ and Mg2+, and enriched in Si, alkalinity, Ca2+, Sr2+, Mn, NH4+, PO43− and H2S, relative to surrounding seawater. The compositions of the warm fluid samples collected in and around the cave define mixing lines which suggest dilution of a single thermal fluid (T ≥ 23°C) by cool overlying seawater (T= 17–17.6°C). The chemical data suggest that the proposed thermal fluid contains two components, one derived from seawater (< 90%) and the other from low-salinity groundwater (> 10%). Excess Si, alkalinity, Ca2+, Sr2+ and Mn relative to seawater are likely derived from the groundwater component or dissolution/hydrothermal alteration of the host rocks. Magnesium has been removed from the seawater component in exchange for Ca2+, due to dolomitisation of the limestone and/or hydrothermal alteration reactions. Saturation-state calculations suggest that the vented fluids are near saturation with respect to calcite and supersaturated with respect to dolomite. This and the presence of dolomite in the host rocks and cave-floor sediments suggest that “mixing-zone” dolomitisation of the limestones is occurring, perhaps kinetically assisted by elevated temperature and/or bacterial mediation in the reducing subseafloor zone. One possible “end-member” condition is considered for the thermal fluid — zero-Mg — which suggests an end-member temperature of 50.5°C and a fluid composition derived from ∼ 38% seawater and ∼ 62% groundwater. The heat source for the circulating fluids is uncertain, but may involve warm underlying igneous rocks or heating via the geothermal gradient. A continuous in-situ record of vent-fluid temperature, salinity, pH and O2 concentration collected within the cavern is consistent with our interpretation of the fluid origin, and suggests that tidal forcing affects circulation and venting of the warm fluids.
AT the surface of sulphide-rich marine and freshwater sediments, the gliding filamentous sulphur bacteria Beggiatoa spp. often grow abundantly to form conspicuous white mats1-6. Beggiatoa may be responsible for the whole benthic consumption of oxygen, converting sulphide to either intracellular elemental sulphur, or to extracellular sulphate7-9. Various strains of Beggiatoa have shown a capacity for nitrogen fixation and assimilation of ammonium and nitrate10. We now report that denitrification activity may also be attributed to Beggiatoa spp., which indicates that Beggiatoa mats could have a key role in the benthic cycling of oxygen, sulphur and nitrogen. Microprofiles of nitrate through a Beggiatoa mat on a lake sediment showed that all nitrate taken up from the water phase was consumed within the upper 150 mu m of the mat. Complete denitrification was demonstrated by the conversion of 15NO-3 to 15N2 in semi-purified tufts of Beggiatoa, and the coupling of denitrification and sulphide oxidation was indicated by micro-profiles of oxygen and sulphide in pure cultures.
WHITE web-like 'mats' of the filamentous sulphur-oxidizing bacterium
Beggiatoa are commonly observed on the surface of anoxic
sediments1-3. As a typical interface organism Beggiatoa
requires a source of inorganic reduced sulphur and dissolved free
oxygen. The first pure cultures of marine strains of Beggiatoa were
recently obtained by artificially reconstructing an
O2-H2S interface in a semi-solid medium that
supports the gliding mobility of the filaments4,5. The
maximal thickness of these Beggiatoa mats in culture was 1.0 mm. We now
report the discovery of dense layers of filamentous sulphur-oxidizing
bacteria up to 3 cm thick on the sediment surface, and up to 30 cm thick
between stands of vestimen-tiferan tube worms at the Guaymas Basin
hydrothermal vent site in the Gulf of California at a depth of 2,010 m.
The mats are essentially monocultures of Beggiatoa-type organisms
containing filaments of three width classes, the largest filaments being
116-122 μm in diameter. Freshly collected filaments showed
chemoautotrophic metabolism and active gliding motility. The phenomenon
of a natural mass growth of a bacterium is of great physiological and
ecological interest, and could also be of biotechnical importance
considering the difficulties of mass cultivation of interface organisms
such as Beggiatoa and the other 'large' sulphur-oxidizing bacteria such
as Thiovulum6 and Thioploca7.
Electron micrographs of sections of Thioploca ingrica and of Beggiatoa showed that the wall of both consisted of multiple and similar layers, of which only the innermost took part in septum formation. Thioploca, however, contained an additional wall component. Invaginations of the cytoplasmic membrane produced extensive intracytoplasmic membranes in both organisms. Sulfur appeared to be deposited within this membrane system, which was accentuated in Thioploca by an enclosure of dense, vesicular material. The deposition of sulfur external (in effect) to the cytoplasmic membrane was also found when hydrogen sulfide and air were bubbled through cultures of a number of Gram-negative bacteria not considered to be sulfur bacteria. The cytoplasm of Beggiatoa was richer in ribosomes than the extraordinarily dense cytoplasm of Thioploca, and the lipid deposits of both left behind spaces that were not membrane-bounded. Metachromatic granules were observed only in Beggiatoa. A heterotrophic strain of Beggiatoa contained a diffuse nucleoplasm, but nucleoplasms could not be recognized either in the wild type or in Thioploca. Thioploca and Beggiatoa are sufficiently different in their infrastructure to be considered distinct organisms. The former consistently produce sheaths. Similarities in structure and in the arrangement of components are enough to support a family relationship.
A method is described for determination of biological thiols at the picomole level based upon conversion of thiols to fluorescent derivatives by reaction with monobromobimane and separation of the derivatives by reverse-phase high-performance liquid chromatography. Thiols separated by the procedure include N-acetylcysteine, coenzyme A, coenzyme M, cysteamine, cysteine, cysteinylglycine, ergothioneine, ethanethiol, glutathione, γ-glutamylcysteine, homocysteine, hydrogen sulfide, 2-mercaptoethanol, mercaptopyrimidine, methanethiol, pantetheine, 4′-phosphopantetheine, thiosulfate, and 2-thiouracil. Since monobromobimane has little fluorescence and reacts very selectively with thiols to produce fluorescent derivatives, crude extracts can be derivatized and analyzed without prepurification of the thiols, the entire process requiring only 1 to 2 h. The technique is illustrated by determination of the thiol levels in red blood cells.
Microbial mats discovered in a ground-water ecosystem in southern Romania contain chemoautotrophic bacteria that fix inorganic carbon, using hydrogen sulfide as an energy source. Analysis of stable carbon and nitrogen isotopes showed that this chemoautotrophic production is the food base for 48 species of cave-adapted terrestrial and aquatic invertebrates, 33 of which are endemic to this ecosystem. This is the only cave ecosystem known to be supported by in situ autotrophic production, and it contains the only terrestrial community known to be chemoautotrophically based.
A microscopic survey is presented of the most commonly observed and morphologically conspicuous microorganisms found attached to natural surfaces or to artificial materials deposited in the immediate vicinity of thermal submarine vents at the Galapagos Rift ocean spreading zone at a depth of 2,550 meters. Of special interest were the following findings: (i) all surfaces intermittently exposed to H(2)S-containing hydrothermal fluid were covered by layers, ca. 5 to 10 mum thick, of procaryotic, gram-negative cells interspaced with amorphous metal (Mn-Fe) deposits; (ii) although some of the cells were encased by dense metal deposits, there was little apparent correlation between metal deposition and the occurrence of microbial mats, (iii) highly differentiated forms appeared to be analogues of certain cyanobacteria, (iv) isolates from massive mats of a prosthecate bacterium could be identified as Hyphomicrobium spp., (v) intracellular membrane systems similar to those found in methylotrophic and nitrifying bacteria were observed in approximately 20% of the cells composing the mats, (vi) thiosulfate enrichments made from mat material resulted in isolations of different types of sulfur-oxidizing bacteria including the obligately chemolithotrophic genus Thiomicrospira.
Filamentous bacteria, identified as members of the genus Beggiatoa by gliding motility and internal globules of elemental sulfur, occur in massive aggregations at the deep-sea hydrothermal vents of the Guaymas Basin, Gulf of California. Cell aggregates covering the surface of sulfide-emanating sediments and rock chimneys were collected by DS R/V Alvin and subjected to shipboard and laboratory experiments. Each sample collected contained one to three discrete width classes of this organism usually accompanied by a small number of "flexibacteria" (width, 1.5 to 4 mum). The average widths of the Beggiatoa classes were 24 to 32, 40 to 42, and 116 to 122 mum. As indicated by electron microscopy and cell volume/protein ratios, the dominant bacteria are hollow cells, i.e., a thin layer of cytoplasm surrounding a large central liquid vacuole. Activities of Calvin-cycle enzymes indicated that at least two of the classes collected possess autotrophic potential. Judging from temperature dependence of enzyme activities and whole-cell CO(2) incorporation, the widest cells were mesophiles. The narrowest Beggiatoa sp. was either moderately thermophilic or mesophilic with unusually thermotolerant enzymes. This was consistent with its occurrence on the flanks of hot smoker chimneys with highly variable exit temperatures. In situ CO(2) fixation rates, sulfide stimulation of incorporation, and autoradiographic studies suggest that these Beggiatoa spp. contribute significantly as lithoautrophic primary producers to the Guaymas Basin vent ecosystems.
Sea caves as model systems for energy flow studies in primary hard bottom communities
- J A Ott
- A Svoboda
Ott JA, Svoboda A (1976) Sea caves as model systems for
energy flow studies in primary hard bottom communities.
Pubbl Staz zool Napoli 40:477-485
Biometry: the principles and prac-tice of statistics in biological research Oxidation of reduced sulphur com-pounds in volcanic regions in Bay of Plenty (New Zealand) and Matupy Harbour (New Britain, Papua-New Guinea) (in Russian)
- Sokal Rr
- Freeman
Sokal RR, Rohlf FJ (1981) Biometry: the principles and prac-tice of statistics in biological research. W H Freeman, San Francisco 32. Sorokin D Yu (1991) Oxidation of reduced sulphur com-pounds in volcanic regions in Bay of Plenty (New Zealand) and Matupy Harbour (New Britain, Papua-New Guinea) (in Russian). Proc Acad Sci USSR Ser Biol 3:376–387
Composition of microbial mats from a submarine cave with shallow hydrothermal vents at Capo Palinuro, Southern Italy
- R G Mattison
- P R Dando
Mattison RG, Dando PR (1994) Composition of microbial
mats from a submarine cave with shallow hydrothermal vents
at Capo Palinuro, Southern Italy. BRIDGE Newslett 7:10-11
- Jm Larkin
- Wr Strohl
- Beggiatoa
- Thioploca Thiothrix
Larkin JM, Strohl WR (1983) Beggiatoa, Thiothrix, and Thioploca. Annu Rev Microbiol 37:341–367
Microbial mats: a joint venture
- H Gemerden
- Van
Gemerden H van (1993) Microbial mats: a joint venture. Mar
Geol 113:3-25
- J M Larkin
- Thiothrix Beggiatoa
Larkin JM, Strohl WR (1983) Beggiatoa, Thiothrix, and Thioploca. Annu Rev Microbiol 37:341-367
Shallow water gasohydrothermal vents of Ushishir Volcano and the ecosystem of Kraternaya Bight (the Kurile Islands)
- V G Tarasov
- M V Propp
- L N Propp
- A V Zhirmunsky
- B B Namsaraev
- V M Gorlenko
- D A Starynin
Tarasov VG, Propp MV, Propp LN, Zhirmunsky AV, Namsaraev BB, Gorlenko VM, Starynin DA (1990) Shallow water
gasohydrothermal vents of Ushishir Volcano and the ecosystem of Kraternaya Bight (the Kurile Islands). Mar Ecol 11:
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