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Map of Obsidian Pool (north at top) showing the relation between Obsidian Pool (darker blue) and the larger hot spring (lighter blue) it flows into, as well as sample locations (mapping by Bob Osburn). Sample numbers reflect the date that each sample was taken in year-month-day notation. Splayed hachures indicate descending slopes to the springs from the surrounding meadow, and main gas sources are indicated in the central and southern areas of the hot spring. Dark outline of Obsidan Pool indicates the water edge in 1999. Water levels change with time, as suggested by the pictures in Figure 2.
Contexts in source publication
Context 1
... Pool (Figure 1) is a persistent hot spring south of Goose Lake in the Mud Volcano Area, which is located to the southwest of the Sour Creek resurgent dome within the Yellowstone Caldera (Christiansen 2001). Though the pool is relatively shallow (10-100 cm) and varies in size somewhat from year to year (see Figure 2, next page), our time series of measurements (see below) shows that the pool temperature and pH are relatively constant at 78.9 o C ± 4.0 o and 6.7 pH ± 0.4, respectively (90% confidence intervals). ...
Context 2
... of this type are shown in Figure 3 for all of the 182 energy- Corresponding chemical reactions are identified and correlated to this diagram in the Appendix (page 12). Affinities, calculated with analytical data in Tables 1 and 2, together with equilibrium constants for each reaction, are color-coded by oxidant (electron acceptor) using symbols that correspond to the samples from the locations shown in Figure 1. The scatter of points for a single reaction reflects the natural variation of the hot spring system. ...
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Citations
... The amount of chemical energy potentially available for chemolithoautotrophic metabolism in the Pisciarelli thermal waters was evaluated on the basis of thermodynamic modeling (e.g. Amend and Shock 2001, Amend et al. 2003, Shock et al. 2005, Price et al. 2015, Amend and LaRowe 2019, Casar et al. 2020) by comparing the natural state of the system with the corresponding equilibrium state for 320 reactions involving H-, O-, C-, N-, S-and Febearing species (Supplementary Table S1). Values of Gibbs free energy ( G r , in J mol −1 ) were calculated as: ...
Although terrestrial hydrothermal systems are considered among the most fascinating environments, how their unique and extreme conditions can affect microorganisms selection and the role in biogeochemical cycles has not yet been well elucidated. A combined geochemical and microbiological exploration in waters and sediments from ten sampling points along a sharp temperature gradient (15–90 °C) within an extremely acidic hydrothermal system (Pisciarelli Spring, Campi Flegrei area, southern Italy) displayed how hydrothermal fluids influence the microbial dynamics. This area was characterized by high levels of reduced gaseous species (e.g. H2S, H2, CH4, CO), and very low pH values (<2.3). Thermodynamic calculations revealed a high microbial catabolic potential in oxidation/reduction reactions of N-, S-, and Fe-bearing species. Overall, an increase of the archaeal/bacterial abundance ratio was observed by decreasing temperature and pH values. In particular, Archaea and Bacteria were present in almost equal cell abundance (up to 1.1 × 109 and 9.3 × 108 cell/g, respectively) in the <70 °C sampling points (average pH = 2.09); on the contrary, highest temperature waters (85–90 °C; average pH = 2.26) were characterized by low abundance of archaeal cells. The high-throughput sequencing of 16S rRNA gene indicated strong differences in archaeal and bacterial communities’ composition along temperature gradient. However, the microbiome in this extreme environment was mainly constituted by chemoautotrophic microorganisms that were likely involved in N-, S-, and Fe-bearing species transformations (e.g. Acidianus infernus, Ferroplasma acidarmanus, Acidithiobacillus, Sulfobacillus, Thaumarchaeota), in agreement with thermodynamic calculations.
... GOPA itself is roughly 1 km 2 and drains into Goose Lake and its outflow stream to the north. Due to the rich biodiversity and geochemical gradients, GOPA is often used as a study site for microbial phylogenetics as well as geothermal research (Barns et al., 1994;Hugenholtz et al., 1998;Meyer-Dombard et al., 2005;Shock et al., 2005;Spear et al., 2005;Havig, 2009;Berelson et al., 2011;Mata et al., 2012;Pepe-Ranney et al., 2012). ...
Microbial communities in hydrothermal systems exist in a range of macroscopic morphologies including stromatolites, mats, and filaments. The architects of these structures are typically autotrophic, serving as primary producers. Structures attributed to microbial life have been documented in the rock record dating back to the Archean including recent reports of microbially-related structures in terrestrial hot springs that date back as far as 3.5 Ga. Microbial structures exhibit a range of complexity from filaments to more complex mats and stromatolites and the complexity impacts preservation potential. As a result, interpretation of these structures in the rock record relies on isotopic signatures in combination with overall morphology and paleoenvironmental setting. However, the relationships between morphology, microbial community composition, and primary productivity remain poorly constrained. To begin to address this gap, we examined community composition and carbon fixation in filaments, mats, and stromatolites from the Greater Obsidian Pool Area (GOPA) of the Mud Volcano Area, Yellowstone National Park, WY. We targeted morphologies dominated by bacterial phototrophs located in close proximity within the same pool which are exposed to similar geochemistry as well as bacterial mat, algal filament and chemotrophic filaments from nearby springs. Our results indicate (i) natural abundance δ¹³C values of biomass from these features (−11.0 to −24.3‰) are similar to those found in the rock record; (ii) carbon uptake rates of photoautotrophic communities is greater than chemoautotrophic; (iii) oxygenic photosynthesis, anoxygenic photosynthesis, and chemoautotrophy often contribute to carbon fixation within the same morphology; and (iv) increasing phototrophic biofilm complexity corresponds to a significant decrease in rates of carbon fixation—filaments had the highest uptake rates whereas carbon fixation by stromatolites was significantly lower. Our data highlight important differences in primary productivity between structures despite indistinguishable δ¹³C values of the biomass. Furthermore, low primary productivity by stromatolites compared to other structures underscores the need to consider a larger role for microbial mats and filaments in carbon fixation and O2 generation during the Archean and Proterozoic.
... Terrestrial hot springs host a variety of thermophilic microorganisms, which perform numerous redox processes including CO oxidation and thus play important roles in many geochemical cycles (Amend and Shock 2001;Shock et al. 2005). Over the last decade, many 16S rRNA genebased phylogenetic studies have investigated microbial communities in terrestrial hot springs from a variety of locations, such as Tibet, China (Yim et al. 2006;Huang et al. 2011;Wang et al. 2013), Yunnan Province, China Song et al. 2013), Thailand (Purcell et al. 2007), Yellowstone National Park, USA Miller et al. 2009; ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 5 Kozubal et al. 2013), Great Basin, USA (Costa et al. 2009;Cole et al. 2013), the Philippines , and Canada and New Zealand (Sharp et al. 2014). ...
Accumulating genomic evidence suggests that a variety of thermophilic bacteria contain cox operons and may be capable of aerobic carbon monoxide (CO) oxidation. However, little is known about the distribution and diversity of the cox-encoding (COXE) bacteria in natural geothermal environments. In this study, we examined coxL gene (encoding the large subunit of carbon monoxide dehydrogenase: CoxL) sequences retrieved from the sediments of twenty-five geothermal sites located in the Qinghai-Tibetan Plateau (QTP) and Yunnan Province (YP) of China, the Bacon-Manito Geothermal Production Field (BGPF) of the Philippines, and the Great Basin of the U.S. (USGB). Temperature and pH ranges of the studied hot springs were 22.1 to 90.8°C and 2.7 to 9.4, respectively. Phylogenetic analyses showed that most CoxL sequences were closely related to the classes Actinobacteria, Deinococci, Ktedonobacteria, Thermomicrobia, and Clostridia, and hot springs from different regions hosted different COXE communities. In addition, these hot springs harbored some COXE bacteria that were phylogenetically distinct from those inhabiting non-geothermal ecosystems. This study revealed no significant correlation between temperature or pH and the composition or diversity of COXE communities at the global scale. However, within a given region, temperature was correlated with the COXE bacterial community composition.
... One distinctive feature in geothermal systems is that deeply-sourced, hot, reducing fluids discharged along fractures interact with cool, oxidized environments near the Earth's surface, creating steep redox and temperature gradients . Thermophilic microbes exploit such chemical disequilibria to harvest metabolic energy in accordance with their intrinsic physiological capabilities (Meyer-Dombard et al. 2005; Shock et al. 2005; D'Imperio et al. 2008 ). Microbially-mediated processes would have to compete with abiotic oxidation for reduced constituents released from the source fluid. ...
Geothermal environments are characterized by dynamic redox and temperature fluctuations inherited from the exposure of deeply-sourced, hot, reducing fluids to low-temperature, oxidizing ambient environments. To investigate whether microbial assemblages shifted in response to the changes of a redox state within acidic hot ponds, we collected three paired water and sediment samples from the Tatun Volcano Group, assessed metabolic roles of community members, and correlated their functional capabilities with geochemical factors along depth. Molecular analyses revealed that Sulfolobus spp., Acidianus spp. and Vulcanisaeta spp. capable of respiring elemental sulfur under oxic and/or low-oxygen conditions were the major archaeal members in planktonic communities. In contrast, obligate anaerobic Caldisphaera spp. dominated over others in bottom-dwelling communities. Bacteria were only detected in one locality wherein the majority was affiliated with microaerophilic Hydrogenobaculum spp. Cluster analyses indicated that archaeal communities associated with sediments tended to cluster together and branch off those with water. In addition, the quantities of dissolved oxygen within the water column were substantially less than those in equilibrium with atmospheric oxygen, indicating a net oxygen consumption most likely catalyzed by microbial processes. These lines of evidence suggest that the segregation of planktonic from bottom-dwelling archaeal assemblages could be accounted for by the oxygen affinities inherited in individual archaeal members. Community assemblages in geothermal ecosystems would be often underrepresented without cautious sampling of both water and sediments.
... Selected sediment and microbial mat samples were analyzed using scanning electron microscopy (Phillips Field Emission-SEM) in combination with energy-dispersive analysis of x-rays (EDAX) as well as x-ray diffraction (XRD). Thermodynamic calculations adjusted for temperature effects and performed using site-specific activities of dissolved and solid-phase constituents (Amend and Shock, 2001 ) showed that numerous oxidation-reduction reactions are exergonic (i.e., energy-yielding) in these types of geothermal systems and could support chemolitho-or chemoorganotrophic metabolisms (Amend et al., 2003; Inskeep et al., 2005; Shock et al., 2005 ). The oxidation of energy-rich, reduced constituents such as H 2 , CH 4 , H 2 S, S 0 , and As(III) is extremely favorable when geothermal waters are exposed to atmospheric O 2 , or in some cases using alternate electron acceptors such as nitrate, ferric Fe, sulfate, or elemental S 0 . ...
The Yellowstone geothermal complex contains over 10,000 diverse geothermal features that host numerous phylogenetically deeply rooted and poorly understood archaea, bacteria, and viruses. Microbial communities in high-temperature environments are generally less diverse than soil, marine, sediment, or lake habitats and therefore offer a tremendous opportunity for studying the structure and function of different model microbial communities using environmental metagenomics. One of the broader goals of this study was to establish linkages among microbial distribution, metabolic potential, and environmental variables. Twenty geochemically distinct geothermal ecosystems representing a broad spectrum of Yellowstone hot-spring environments were used for metagenomic and geochemical analysis and included approximately equal numbers of: (1) phototrophic mats, (2) "filamentous streamer" communities, and (3) archaeal-dominated sediments. The metagenomes were analyzed using a suite of complementary and integrative bioinformatic tools, including phylogenetic and functional analysis of both individual sequence reads and assemblies of predominant phylotypes. This volume identifies major environmental determinants of a large number of thermophilic microbial lineages, many of which have not been fully described in the literature nor previously cultivated to enable functional and genomic analyses. Moreover, protein family abundance comparisons and in-depth analyses of specific genes and metabolic pathways relevant to these hot-spring environments reveal hallmark signatures of metabolic capabilities that parallel the distribution of phylotypes across specific types of geochemical environments.
... Microbes use a wide range of redox reactions to obtain energy for growth and therefore have a significant impact on the biogeochemical cycling of elements including carbon, nitrogen, and sulfur (Falkowski et al., 2008). Free energy calculations using geochemical analyses of an environment demonstrate that the most energetically-favorable redox reactions vary depending on the local chemistry and temperature (Amend and Shock, 2001; Shock et al., 2005 Shock et al., , 2010 McCollom, 2007; Amend et al., 2011). Such calculations can be used to assess the habitability of diverse environments on Earth, or other planetary bodies such as Mars and Europa (Hoehler, 2007). ...
We combined free energy calculations and metagenomic analyses of an elemental sulfur (S0) deposit on the surface of Borup Fiord Pass Glacier in the Canadian High Arctic to investigate whether the energy available from different redox reactions in an environment predicts microbial metabolism. Many S, C, Fe, As, Mn and NH4+ oxidation reactions were predicted to be energetically feasible in the deposit, and aerobic oxidation of S0 was the most abundant chemical energy source. Small subunit ribosomal RNA (SSU rRNA) gene sequence data showed that the dominant phylotypes were Sulfurovum and Sulfuricurvum, both Epsilonproteobacteria known to be capable of sulfur lithotrophy. Sulfur redox genes were abundant in the metagenome, but sox genes were significantly more abundant than reverse dsr genes. Interestingly, there appeared to be habitable niches that were unoccupied at the depth of genome coverage obtained. Photosynthesis and NH4+ oxidation should both be energetically favorable, but we found few or no functional genes for oxygenic or anoxygenic photosynthesis, or for NH4+ oxidation by either oxygen (nitrification) or nitrite (anammox). The free energy, SSU rRNA gene and quantitative functional gene data are all consistent with the hypothesis that sulfur-based chemolithoautotrophy by Epsilonproteobacteria (Sulfurovum and Sulfuricurvum) is the main form of primary productivity at this site, instead of photosynthesis. This is despite the presence of 24-hour sunlight, and the fact that photosynthesis is not known to be inhibited by any of the environmental conditions present. This is the first time that Sulfurovum and Sulfuricurvum have been shown to dominate a sub-aerial environment, rather than anoxic or sulfidic settings. We also found that Flavobacteria dominate the surface of the sulfur deposits. We hypothesize that this aerobic heterotroph uses enough oxygen to create a microoxic environment in the sulfur below, where the Epsilonproteobacteria can flourish.
... Selected sediment and microbial mat samples were analyzed using scanning electron microscopy (Phillips Field Emission-SEM) in combination with energy-dispersive analysis of x-rays (EDAX) as well as x-ray diffraction (XRD). Thermodynamic calculations adjusted for temperature effects and performed using site-specific activities of dissolved and solid-phase constituents (Amend and Shock, 2001) showed that numerous oxidation-reduction reactions are exergonic (i.e., energy-yielding) in these types of geothermal systems and could support chemolitho-or chemoorganotrophic metabolisms (Amend et al., 2003;Inskeep et al., 2005;Shock et al., 2005). The oxidation of energy-rich, reduced constituents such as H 2 , CH 4 , H 2 S, S 0 , and As(III) is extremely favorable when geothermal waters are exposed to atmospheric O 2 , or in some cases using alternate electron acceptors such as nitrate, ferric Fe, sulfate, or elemental S 0. Dissolved Fe(II) and ammonium (NH 4 ) concentrations can be very high in certain YNP geothermal systems, and offer yet another set of exergonic reactions that serve as a potential geochemical niche for chemotrophic organisms. ...
YNP metagenome project steering committee and working group members and their respective contributions are listed in Table S1 in Supplementary Material. The Yellowstone geothermal complex contains over 10,000 diverse geothermal features that host numerous phylogenetically deeply rooted and poorly understood archaea, bac-teria, and viruses. Microbial communities in high-temperature environments are generally less diverse than soil, marine, sediment, or lake habitats and therefore offer a tremen-dous opportunity for studying the structure and function of different model microbial communities using environmental metagenomics. One of the broader goals of this study was to establish linkages among microbial distribution, metabolic potential, and envi-ronmental variables. Twenty geochemically distinct geothermal ecosystems representing a broad spectrum of Yellowstone hot-spring environments were used for metagenomic and geochemical analysis and included approximately equal numbers of: (1) phototrophic mats, (2) "filamentous streamer" communities, and (3) archaeal-dominated sediments. The metagenomes were analyzed using a suite of complementary and integrative bioin-formatic tools, including phylogenetic and functional analysis of both individual sequence reads and assemblies of predominant phylotypes.This volume identifies major environmen-tal determinants of a large number of thermophilic microbial lineages, many of which have not been fully described in the literature nor previously cultivated to enable functional and genomic analyses. Moreover, protein family abundance comparisons and in-depth analyses of specific genes and metabolic pathways relevant to these hot-spring environments reveal hallmark signatures of metabolic capabilities that parallel the distribution of phylotypes across specific types of geochemical environments.
... Based on aerial photos from January 2009, we infer that in winter months snow accumulates along the margins of the thermal area, but not in the center. The OPTA hosts several thermal pools with measured water temperatures between 21.9 C and 84.0 C (Table 1) with mainly acid-sulfate composition and low chloride concentrations [Shock et al., 2005]. All of the pools are bubbling and have temperatures that are below the boiling point of pure water suggesting influx of a CO 2 rich gas. ...
Characterizing the vigor of magmatic activity in Yellowstone requires knowledge of
the mechanisms and rates of heat transport between magma and the ground surface. We
present results from a heat flow study in two vapor dominated, acid-sulfate thermal areas in
the Yellowstone Caldera, the 0.11 km2 Obsidian Pool Thermal Area (OPTA) and the
0.25 km2 Solfatara Plateau Thermal Area (SPTA). Conductive heat flux through a low
permeability layer capping large vapor reservoirs is calculated from soil temperature
measurements at >600 locations and from laboratory measurements of soil properties.
The conductive heat output is 3.6 � 0.4 MW and 7.5 � 0.4 MW from the OPTA and
the SPTA, respectively. The advective heat output from soils is 1.3 � 0.3 MW and
1.2 � 0.3 MW from the OPTA and the SPTA, respectively and the heat output from
thermal pools in the OPTA is 6.8 � 1.4 MW. These estimates result in a total heat
output of 11.8 � 1.4 MW and 8.8 � 0.4 MW from OPTA and SPTA, respectively.
Focused zones of high heat flux in both thermal areas are roughly aligned with regional
faults suggesting that faults in both areas serve as conduits for the rising acid vapor.
Extrapolation of the average heat flux from the OPTA (103 � 2 W�m�2) and SPTA
(35 � 3 W�m�2) to the �35 km2 of vapor dominated areas in Yellowstone yields 3.6
and 1.2 GW, respectively, which is less than the total heat output transported by
steam from the Yellowstone Caldera as estimated by the chloride inventory method
(4.0 to 8.0 GW).
... Reactions corresponding to anaerobic respiration of nitrate, sulfate, and carbon dioxide were also evaluated. The reduction of sulfate (29.9 kJ mol À1 e À ) or nitrate (29.7 kJ mol À1 e À ) utilizing dissolved hydrogen as the reductant was nearly equivalent, which has not typically been observed in geothermal systems or predicted by evaluation of reduction half-reaction potentials (Amend & Shock, 2001; Inskeep et al., 2005; Shock et al., 2005; Spear et al., 2005). The energy gained from sulfide oxidizing denitrification to NH þ 4 (1.03 kJ mol À1 e À ) or N 2 (aq)(À1.54 ...
... If the residence time within HBS is lower than the rate of microbial respiration, these two species may serve as the dominant electron donors for aerobic lithotrophy within the water column. Within Obsidian Pool YNP, nitrite and ammonia oxidation were calculated to be the least exergonic aerobic respirations, yielding less than half the energy of reactions involving the oxidation of hydrogen, sulfides, metals, etc. (Shock et al., 2005). In stark contrast to Obsidian Pool, both nitrification reactions in HBS are more favorable, even compared to sulfide oxidation. ...
Water chemistry, energetic modeling, and molecular analyses were combined to investigate the microbial ecology of a biofilm growing in a thermal artesian spring within Hot Springs National Park, AR. This unique fresh water spring has a low dissolved chemical load and is isolated from both light and direct terrestrial carbon input - resulting in an oligotrophic ecosystem limited for fixed carbon and electron donors. Evaluation of energy yields of lithotrophic reactions putatively linked to autotrophy identified the aerobic oxidation of methane, hydrogen, sulfide, ammonia, and nitrite as the most exergonic. Small subunit (SSU) rRNA gene libraries from biofilm revealed a low-diversity microbial assemblage populated by bacteria and archaea at a gene copy ratio of 45:1. Members of the bacterial family 'Nitrospiraceae', known for their autotrophic nitrite oxidation, dominated the bacterial SSU rRNA gene library (approximately 45%). Members of the Thaumarchaeota ThAOA/HWCGIII (>96%) and Thaumarchaeota Group I.1b (2.5%), which both contain confirmed autotrophic ammonia oxidizers, dominated the archaeal SSU rRNA library. Archaea appear to dominate among the ammonia oxidizers, as only ammonia monooxygenase subunit A (amoA) genes belonging to members of the Thaumarchaeota were detected. The geochemical, phylogenetic, and genetic data support a model that describes a novel thermophilic biofilm built largely by an autotrophic nitrifying microbial assemblage. This is also the first observation of 'Nitrospiraceae' as the dominant organisms within a geothermal environment.
... source. Its name comes from the black sand deposited at the bottom of the pool, probably volcanic glass coated with pyrite (Shock et al., 2005). In the 1990s, the group of Norman Pace described the microbial community of Obsidian Pool by constructing clone libraries of 16S rRNA genes amplified from DNA extracts of water and sediment (Barns et al., 1994; Hugenholtz et al., 1998). ...
In 1998, a cultivation-independent survey of the microbial community in Obsidian Pool, Yellowstone National Park, detected 12 new phyla within the Domain Bacteria. These were dubbed 'candidate divisions' OP1 to OP12. Since that time the OP10 candidate division has been commonly detected in various environments, usually as part of the rare biosphere, but occasionally as a predominant community component. Based on 16S rRNA gene phylogeny, OP10 comprises at least 12 class-level subdivisions. However, despite this broad ecological and evolutionary diversity, all OP10 bacteria have eluded cultivation until recently. In 2011, two reference species of OP10 were taxonomically validated, removing the phylum from its 'candidate' status. Construction of a highly resolved phylogeny based on 29 universally conserved genes verifies its standing as a unique bacterial phylum. In the following paper we summarize what is known and what is suspected about the newest described bacterial phylum, the Armatimonadetes.
