Figure 3 - uploaded by Myriam Bormans
Content may be subject to copyright.
Quantitative data of cell size (A), cellular abundance of cyanophycin globule (B) and the size of cyanophycin globule (C) in vegetative cells and akinetes (filament-attached and -free) in A. ovalisporum incubated under akinete-inducing conditions. Samples collected at different times during the induction (D0, D4, D7, D9, and D14, represent sampling days) were stained by Sakaguchi reaction and CG became dark visible (as presented in ). Data was collected by analyzing microscopic images using ImageJ, image-processing program. Bars present average and standard deviation. For each time point and cell type at least 40 individual objects were analyzed.
Source publication
Akinetes are spore-like non-motile cells that differentiate from vegetative cells of filamentous cyanobacteria from the order Nostocales. They play a key role in the survival and distribution of these species and contribute to their perennial blooms. Here, we demonstrate variations in cellular ultrastructure during akinete formation concomitant wit...
Contexts in source publication
Context 1
... akinetes matured and detached from the filament, they further accumulated CG of variable sizes and quantities, as also observed in electron micrographs (Figure 1, D21). Images collected during the akinete differentiation process were quantitatively analyzed for cell size (expressed in aerial units extracted from 2D images) and for CG cellular abundance and size (Figure 3). Upon exposure to akinete-inducing conditions, the size of vegetative cells initially increased but as akinetes formed, vegetative cells shrank back to their original size ( Figure 3A). ...
Context 2
... collected during the akinete differentiation process were quantitatively analyzed for cell size (expressed in aerial units extracted from 2D images) and for CG cellular abundance and size (Figure 3). Upon exposure to akinete-inducing conditions, the size of vegetative cells initially increased but as akinetes formed, vegetative cells shrank back to their original size ( Figure 3A). Filament-attached and -free akinetes appeared 7 days (D7) post-induction and their size was 3-5 times larger than vegetative cells. ...
Context 3
... and -free akinetes appeared 7 days (D7) post-induction and their size was 3-5 times larger than vegetative cells. CG (ca. 4 per cell) were observed in vegetative cells 3 days post-induction and their density substantially reduced (less than 1 per cell) as akinetes formed on day 7, and slightly increased later on ( Figure 3B). The average size of the CG accumulated in vegetative cells during the early stage of akinete induction decreased significantly, as akinetes formed (from ca. 7 to less than 4 μm 2 , Figure 3C). ...
Context 4
... (ca. 4 per cell) were observed in vegetative cells 3 days post-induction and their density substantially reduced (less than 1 per cell) as akinetes formed on day 7, and slightly increased later on ( Figure 3B). The average size of the CG accumulated in vegetative cells during the early stage of akinete induction decreased significantly, as akinetes formed (from ca. 7 to less than 4 μm 2 , Figure 3C). Filament-attached akinete contained between 5-and 10-fold more CG than the vegetative cells whereas free akinetes contained more CG than attached akinetes. ...
Context 5
... average size of the CG accumulated in akinetes was 2-3 times larger than in vegetative cells. The average size of the CG accumulated in free akinetes 14 days post-induction (D14) was significantly larger (p < 0.05, n = 15) than in attached akinetes (Figures 3B,C). ...
Context 6
... akinete induction conditions, CG accumulated in vegetative cells, 4 days post-induction. These C/N storage pools diminished as one of the adjacent vegetative cells initiated its differentiation to an akinete, concomitant with substantial increase in cyanophycin granules inside the developing akinete (Figures 1-3). For example the average calculated CG pool of a vegetative cell, 4 days post-induction was about 2 μm 3 (representing 1.5 % of the total cell volume). ...
Similar publications
Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) generates 3D datasets optimally suited for segmentation of cell ultrastructure and automated connectome tracing but is limited to small fields of view and is therefore incompatible with the new generation of ultrafast multibeam SEMs. In contrast, section-based techniques are multibeam-compatib...
This research aimed to morphological and ultrastructure studies of Lime peels (Citrus aurantifolia (Christm.) Swingle) in citrus diseases. Therefore, the application of microscopic techniques to examine the infestation of pathogens in plants in order to gain further insights into the deterioration of cells at the cellular and subcellular level in p...
Aim
To investigate the role of endoplasmic reticulum stress (ERS)-induced autophagy in Inflammatory bowel disease (IBD) and the intervention mechanism of Portulaca oleracea L. (POL) extract, a medicinal herb with anti-inflammatory, antioxidant, immune-regulating and antitumor properties, in vitro and in vivo.
Materials and Methods
An IL-10-deficie...
Due to the ever-increasing burden of antimicrobial-resistant (AMR) bacteria, the development of novel antimicrobial agents and biomaterials to act as carriers and/or potentiate antimicrobial activity is essential. This study assessed the antimicrobial efficacy of the following ionic metals, silver, gold, palladium, platinum, zinc, and gallium alone...
This study attempts to provide information on ultra-structure of the gut-secretory cells of young whipfin mojarra fish, Gerres filamentosus (Cuvier, 1829) to its functionality where their habitat in a near shore species off Hurghada , Red Sea, Egypt. The gut illustrating: esophagus, stomach, four-pyloric caecae, and intestine. Under the transmissio...
Citations
... Although most often described as a nitrogen storage polymer (12), cyanophycin can also be useful as a store of carbon and energy (13)(14)(15). Cyanophycin as a dynamic nitrogen reservoir is beneficial for cells in a variety of conditions (16)(17)(18). For example, nitrogen-fixing cyanobacteria can use it to separate (aerobic) photosynthesis from the strictly anaerobic process of nitrogen fixation. ...
Cyanophycin is a bacterial polymer mainly used for nitrogen storage. It is composed of a peptide backbone of L-aspartate residues with L-arginines attached to their side chains through isopeptide bonds. Cyanophycin is degraded in two steps: Cyanophycinase cleaves the polymer into β-Asp-Arg dipeptides, which are hydrolyzed into free Asp and Arg by enzymes possessing isoaspartyl dipeptide hydrolase activity. Two unrelated enzymes with this activity, isoaspartyl dipeptidase (IadA) and isoaspartyl aminopeptidase (IaaA) have been shown to degrade β-Asp-Arg dipeptides, but bacteria which encode cyanophycin-metabolizing genes can lack iaaA and iadA genes. In this study, we investigate a previously uncharacterized enzyme whose gene can cluster with cyanophycin-metabolizing genes. This enzyme, which we name cyanophycin dipeptide hydrolase (CphZ), is specific for dipeptides derived from cyanophycin degradation. Accordingly, a co-complex structure of CphZ and β-Asp-Arg shows that CphZ, unlike IadA or IaaA, recognizes all portions of its β-Asp-Arg substrate. Bioinformatic analyses showed that CphZ is found in very many proteobacteria and is homologous to an uncharacterized protein encoded in the "arginine/ornithine transport" (aot) operon of many pseudomonas species, including Pseudomonas aeruginosa. In vitro assays show that AotO is indeed a CphZ, and in cellulo growth experiments show that this enzyme and the aot operon allow P. aeruginosa to take up and use β-Asp-Arg as a sole carbon and nitrogen source. Together the results establish the novel, highly specific enzyme subfamily of CphZs, suggesting that cyanophycin is potentially used by a much wider range of bacteria than previously appreciated.
... The developmentally sophisticated formation of desiccation-induced spores (Sukenik et al. 2015), a strategy shared by fungi and several bacterial phyla, represents perhaps an extreme case of all-out late-pulse allocation to reserves (typical of TORs with low a) that enables extremely long ...
The pulse–reserve paradigm (PRP) is central in dryland ecology, although microorganismal traits were not explicitly considered in its inception. We asked if the PRP could be reframed to encompass organisms both large and small. We used a synthetic review of recent advances in arid land microbial ecology combined with a mathematically explicit theoretical model. Preserving the PRPs core of adaptations by reserve building, the model considers differential organismal strategies to manage these reserves. It proposes a gradient of organisms according to their reserve strategies, from nimble responders (NIRs) to torpid responders (TORs). It predicts how organismal fitness depends on pulse regimes and reserve strategies, partially explaining organismal diversification and distributions. After accounting for scaling phenomena and redefining the microscale meaning of aridity, the evidence shows that the PRP is applicable to microbes. This modified PRP represents an inclusive theoretical framework working across life-forms, although direct testing is still needed.
... The developmentally sophisticated formation of desiccation-induced spores (Sukenik et al., 2015) (Setlow, 2007), a strategy shared by fungi and several bacterial phyla, represents perhaps an extreme case of all-out late-pulse allocation to reserves (typical of TORs with low a ) that enables extremely long quiescence periods. The trade-off here is that a relatively long new pulse with copious resources is needed to allow for an equally complex process of germination (Stewart et al., 1981, Dworkin & Shah, 2010 before new resources can be effectively tapped, as predicted by our model. ...
The pulse-reserve paradigm (PRP) is central in dryland ecology, although traits of microorganisms were not explicitly considered in its inception. We asked if the PRP could be reframed to encompass organisms both large and small. We used a synthetic review of recent advances in arid land microbial autoecology combined with a mathematically explicit theoretical model. Preserving the PRPs original core of adaptations by reserve building, the model considers differential organismal strategies to manage these reserves. It proposes a gradient of organisms according to their reserve strategies, from nimble responders (NIRs) to torpid responders (TORs). It predicts how organismal fitness depends on pulse regimes and reserve strategies thus explaining organismal diversification and distribution. After accounting for scaling phenomena and redefining the microscale meaning of aridity, it becomes patent that the PRP is applicable to microbes, and that this modified PRP represents an inclusive theoretical framework working across life-forms.
... Several bloom-forming cyanobacteria such as Microcystis sp., Dolichospermum sp. (formerly Anabaena), Aphanizomenon ovalisporum, and Planktothrix agardhii store N intracellularly as cyanophycin (Sukenik et al., 2015;Van de Waal et al., 2010). Their advantage over eukaryotic algae under N-limiting conditions may be related to cyanophycin (Kurmayer et al., 2016). ...
... Second, cyanophycin is considered to also be accumulated during the N 2 fixation process in diazotrophic cyanobacteria (Watzer and Forchhammer, 2018), but it is unclear whether R. raciborskii can accumulate cyanophycin under a fluctuating N supply (namely, N-sufficient and N-deficient conditions), as has been reported for non-diazotrophic cyanobacteria (Flores et al., 2019). Third, observations on cyanophycin synthesis in cyanobacteria were predominantly conducted under standard laboratory conditions (Burnat et al., 2014;Sukenik et al., 2015;Van de Waal et al., 2010). Thus, probing into the relationship between N concentration and cyanophycin accumulation in natural conditions will provide further insights into the functional significance of cyanophycin in phytoplankton population dynamics. ...
Nutrient storage is considered a critical strategy for algal species to adapt to a fluctuating nutrient supply. Luxury phosphorus (P) uptake into storage of polyphosphate extends the duration of cyanobacterial dominance and their blooms under P deficiency. However, it is unclear whether nitrogen (N) storage in the form of cyanophycin supports persistent cyanobacterial dominance or blooms in the tropics where N deficiency commonly occurs in summer. In this study, we examined genes for cyanophycin synthesis and degradation in Raphidiopsis raciborskii, a widespread and dominant cyanobacterium in tropical waters; and detected the cyanophycin accumulation under fluctuating N concentrations and its ecological role in the population dynamics of the species. The genes for cyanophycin synthesis (cphA) and degradation (cphB) were highly conserved in 21 out of 23 Raphidiopsis strains. This suggested that the synthesis and degradation of cyanophycin are evolutionarily conserved to support the proliferation of R. raciborskii in N-fluctuating and/or deficient conditions. Isotope ¹⁵N-NaNO3 labeling experiments showed that R. raciborskii QDH7 always commenced to synthesize and accumulate cyanophycin under fluctuating N conditions, regardless of whether exogenous N was deficient. When the NO3⁻-N concentration exceeded 1.2 mg•L⁻¹, R. raciborskii synthesized cyanophycin primarily through uptake of ¹⁵N-NaNO3. However, when the NO3⁻-N concentration was below 1.0 mg•L⁻¹, cyanophycin-based N was derived from unlabeled N2, as evidenced by increased dinitrogenase activity. Cells grown under NO3⁻-N < 1.0 mg•L⁻¹ had lower cyanophycin accumulation rates than cells grown under NO3⁻-N > 1.2 mg•L⁻¹. Our field investigation in a large tropical reservoir underscored the association between cyanophycin content and the population dynamics of R. raciborskii. The cyanophycin content was high in N-sufficient (NO3⁻-N > 0.45 mg•L⁻¹) periods, and decreased in N-deficient summer. In summer, R. raciborskii sustained a relatively high biomass and produced few heterocysts (< 1%). These findings indicated that cyanophycin-released N, rather than fixed N, supported persistent R. raciborskii blooms in N-deficient seasons. Our study suggests that the highly adaptive strategy in a N2-fixing cyanobacterial species makes mitigating its bloom more difficult than previously assumed.
... In single-cell cyanobacteria, cyanophycin is synthesized during periods of low light, when aerobic photosynthesis does not occur, and consumed during periods of high light 6 . In multicellular cyanobacteria communities, cyanophycin metabolism can be performed in specialized heterocysts, dedicated cells for fixing nitrogen 8 or spore-like akinetes 9 . The heterocysts generate and store cyanophycin, which is degraded when needed and transferred to vegetative cells that cannot fix nitrogen 10 . ...
Cyanophycin is a natural biopolymer produced by a wide range of bacteria, consisting of a chain of poly-l-Asp residues with l-Arg residues attached to the β-carboxylate sidechains by isopeptide bonds. Cyanophycin is synthesized from ATP, aspartic acid and arginine by a homooligomeric enzyme called cyanophycin synthetase (CphA1). CphA1 has domains that are homologous to glutathione synthetases and muramyl ligases, but no other structural information has been available. Here, we present cryo-electron microscopy and X-ray crystallography structures of cyanophycin synthetases from three different bacteria, including cocomplex structures of CphA1 with ATP and cyanophycin polymer analogs at 2.6 Å resolution. These structures reveal two distinct tetrameric architectures, show the configuration of active sites and polymer-binding regions, indicate dynamic conformational changes and afford insight into catalytic mechanism. Accompanying biochemical interrogation of substrate binding sites, catalytic centers and oligomerization interfaces combine with the structures to provide a holistic understanding of cyanophycin biosynthesis.
... In Anabaena torulosa, akinetes accumulate cyanophycin during their development and decrease the amount of it when mature [Sarma and Khattar, 1986]. Similarly, Aphanizomenon ovalisporum also accumulates cyanophycin during the formation of akinetes induced by potassium starvation [Sukenik et al., 2015]. A previous study by Leganés et al. [1998] showed that cyanophycin granule formation is necessary for the function of heterocysts and akinetes in N. ellipsosporum. ...
Some cyanobacteria of the order Nostocales can form akinetes, spore-like dormant cells resistant to various unfavorable environmental fluctuations. Akinetes are larger than vegetative cells and contain large quantities of reserve products, mainly glycogen and the nitrogen storage polypeptide polymer cyanophycin. Akinetes are enveloped in a thick protective coat containing a multilayered structure and are able to germinate into new vegetative cells under suitable growth conditions. Here, we summarize the significant morphological and physiological changes that occur during akinete differentiation and germination and present our investigation of the physiological function of the storage polymer cyanophycin in these cellular processes. We show that the cyanophycin production is not required for formation and germination of the akinetes in the filamentous cyanobacterium Anabaena variabilis ATCC 29413.
... Cyanophycin (multi-ʟarginyl-poly-ʟ-aspartate) is a non-ribosomal nitrogen-rich copolymer consisting of equimolar amounts of aspartic acid and arginine (Simon and Weathers 1976;Krehenbrink et al. 2002;Obst and Steinbu 2004;Maheswaran et al. 2006). At neutral pH and physiological ionic strength, cyanophycin is insoluble and accumulates in the cytoplasm as membraneless granules Sukenik et al. 2015). Cyanophycin in particular may be interesting because it can be chemically converted into polyaspartic acid (Joentgen et al. 2001), and in this form, it is a renewable alternative for synthetic polyacrylate (Neumann et al. 2005). ...
Several technologies have aimed to recover nitrogen directly from urine. Nitrogen
recovery in these technologies was limited by the mismatch of the nitrogen-phosphorus molar ratio (N:P) of urine, being 30–46:1, and that of the final product, e.g., 1:1 in struvite and 16–22:1 in microalgae biomass. Additionally, the high nitrogen concentrations found in urine can be inhibitive for growth of microorganisms. Cyanobacteria were expected to overcome phosphorus (P) limitation in urine given their ability to store an N-rich polymer called cyanophycin. In this study, it was found that the model cyanobacterium Synechocystis sp. PCC6803 did not experience signifcant growth inhibition when cultivated in synthetic medium with concentrations of 0.5 g ammonium-N L−1. In the case of urea, no inhibition was observed when having it as sole nitrogen source, but it resulted in chlorosis of the cultures when the process reached stationary phase. Synechocystis was successfully cultivated in a medium with 0.5 g ammonium-N L−1 and a N:P ratio of 276:1, showing the N:P fexibility of this biomass, reaching biomass N:P ratios up to 92:1. Phosphorus starvation resulted in cyanophycin accumulation up to 4%. Dilution of the culture in fresh medium with the addition of 118 mg N L−1 and 1.5 mg P L−1 (N:P of 174:1) resulted in a rapid and transient cyanophycin accumulation up to 11%, after which cyanophycin levels rapidly decreased to 3%.
... Under favorable conditions, the primary thalloid body is composed of vegetative cells and photosynthetic cells. However, in adverse conditions, some cells in the filament differentiate to form climate-resistant spores called akinetes (Sukenik et al. 2015). Moreover, the majority of cyanobacterial species develop several thickwalled cells, called heterocysts, after every 9-15 cells at repeated intervals within the filament (Kumar et al. 2010). ...
An innumerable group of microorganisms are associated with plants and present in the phyllosphere, rhizosphere, and endosphere. They produce different metabolites—such as amino acids, proteins, polysaccharides, and vitamins—that affect plant growth and help to improve soil fertility and crop production naturally. Furthermore, among all inhabitants of the rhizosphere, cyanobacteria are among the foremost organisms, with potential to contribute to biological nitrogen fixation. They contain a specialized type of cell (a heterocyst), which is considered the actual site of dinitrogen fixation in cyanobacteria. Bryophyte–cyanobacterial associations are significant sources of nitrogen fixation in terrestrial ecosystems such as boreal forests. Therefore, cyanobacterial inoculants are influential biofertilizers in sustainable agriculture. This chapter describes beneficial aspects of nitrogen fixation by cyanobacteria in the rhizosphere and the role of cyanobacteria in increasing soil fertility, which leads to improved crop productivity.
... The akinetes of the mutant are found to be less stable against any tested stress conditions, except the exposure to cold. Although the mutant develops defective akinetes, they are nevertheless more resistant to extreme environmental influences than vegetative cells due to the presence of the extracellular polysaccharide layer and intracellular adaptations (Argueta and Summers, 2005;Sukenik et al., 2015;Perez et al., 2016). Expectedly, the vegetative cells, which do not have an extra protecting cell envelope, were less resistant to any of the stress factors applied and only able to withstand cold for 20 days of incubation, conditions, which do not mimic cold winter seasons. ...
Anabaena variabilis is a filamentous cyanobacterium that is capable to differentiate specialized cells, the heterocysts and akinetes, to survive under different stress conditions. Under nitrogen limited condition, heterocysts provide the filament with nitrogen by fixing N 2 . Akinetes are spore-like dormant cells that allow survival during adverse environmental conditions. Both cell types are characterized by the presence of a thick multilayered envelope, including a glycolipid layer. While in the heterocyst this glycolipid layer is required for the maintenance of a microoxic environment and nitrogen fixation, its function in akinetes is completely unknown. Therefore, we constructed a mutant deficient in glycolipid synthesis and investigated the performance of heterocysts and akinetes in that mutant strain. We chose to delete the gene Ava_2595 , which is homolog to the known hglB gene, encoding a putative polyketide synthase previously shown to be involved in heterocyst glycolipid synthesis in Anabaena sp. PCC 7120, a species which does not form akinetes. Under the respective conditions, the Ava_2595 null mutant strain formed aberrant heterocysts and akinete-like cells, in which the specific glycolipid layers were absent. This confirmed firstly that both cell types use a glycolipid of identical chemical composition in their special envelopes and, secondly, that HglB is essential for glycolipid synthesis in both types of differentiated cells. As a consequence, the mutant was not able to fix N 2 and to grow under diazotrophic conditions. Furthermore, the akinetes lacking the glycolipids showed a severely reduced tolerance to stress conditions, but could germinate normally under standard conditions. This demonstrates the importance of the glycolipid layer for the ability of akinetes as spore-like dormant cells to withstand freezing, desiccation, oxidative stress and attack by lytic enzymes. Our study established the dual role of the glycolipid layer in fulfilling different functions in the evolutionary-related specialized cells of cyanobacteria. It also indicates the existence of a common pathway involving HglB for the synthesis of glycolipids in heterocysts and akinetes.
... Phytoplankton viability, including their ability to survive under conditions of nutrient stress, has been extensively studied, especially for organisms that produce massive blooms that emerge and decline rapidly (for reviews, see references 10, 11, and 12). For example, some bloom-forming cyanobacteria, such as Aphanizomenon species, produce morphologically distinct spores that show very little photosynthetic activity and yet remain viable in the sediment for long periods of time, providing the inoculum for the next growth season (13). In laboratory cultures of Synechococcus elegantus PCC 7942 and Synechocystis PCC 6803, two unicellular freshwater cyanobacteria, nitrogen starvation results in a programmed process where cells enter a resting stage, enabling them to survive prolonged periods of stress (14,15). ...
... For the terminal concentrations of 15 N and 13 C in the particulate phase (%P t * ), we used the values of 13 C/ 12 C and 15 N/ 14 N that were obtained from the NanoSIMS analysis of the cells. 13 C/ 12 C and 15 N/ 14 N ratios below the natural values resulted in negative uptake values and were treated as zero uptake. ...
Many microorganisms produce resting cells with very low metabolic activity that allow them to survive phases of prolonged nutrient or energy stress. In cyanobacteria and some eukaryotic phytoplankton, the production of resting stages is accompanied by a loss of photosynthetic pigments, a process termed chlorosis. Here, we show that a chlorosis-like process occurs under multiple stress conditions in axenic laboratory cultures of Prochlorococcus , the dominant phytoplankton linage in large regions of the oligotrophic ocean and a global key player in ocean biogeochemical cycles. In Prochlorococcus strain MIT9313, chlorotic cells show reduced metabolic activity, measured as C and N uptake by Nanoscale secondary ion mass spectrometry (NanoSIMS). However, unlike many other cyanobacteria, chlorotic Prochlorococcus cells are not viable and do not regrow under axenic conditions when transferred to new media. Nevertheless, cocultures with a heterotrophic bacterium, Alteromonas macleodii HOT1A3, allowed Prochlorococcus to survive nutrient starvation for months. We propose that reliance on co-occurring heterotrophic bacteria, rather than the ability to survive extended starvation as resting cells, underlies the ecological success of Prochlorococcus .
IMPORTANCE The ability of microorganisms to withstand long periods of nutrient starvation is key to their survival and success under highly fluctuating conditions that are common in nature. Therefore, one would expect this trait to be prevalent among organisms in the nutrient-poor open ocean. Here, we show that this is not the case for Prochlorococcus , a globally abundant and ecologically important marine cyanobacterium. Instead, Prochlorococcus relies on co-occurring heterotrophic bacteria to survive extended phases of nutrient and light starvation. Our results highlight the power of microbial interactions to drive major biogeochemical cycles in the ocean and elsewhere with consequences at the global scale.
