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Andreas Holzinger - One of the best experts on this subject based on the ideXlab platform.
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arctic antarctic and temperate green algae zygnema spp under uv b stress vegetative cells perform better than pre Akinetes
Protoplasma, 2018Co-Authors: Andreas Holzinger, Siegfried Aigner, Kateřina Trumhova, Philippe Schmittkopplin, Andreas Albert, Martina PichrtovaAbstract:Species of Zygnema form macroscopically visible mats in polar and temperate terrestrial habitats, where they are exposed to environmental stresses. Three previously characterized isolates (Arctic Zygnema sp. B, Antarctic Zygnema sp. C, and temperate Zygnema sp. S) were tested for their tolerance to experimental UV radiation. Samples of young vegetative cells (1 month old) and pre-Akinetes (6 months old) were exposed to photosynthetically active radiation (PAR, 400–700 nm, 400 μmol photons m−2 s−1) in combination with experimental UV-A (315–400 nm, 5.7 W m−2, no UV-B), designated as PA, or UV-A (10.1 W m−2) + UV-B (280–315 nm, 1.0 W m−2), designated as PAB. The experimental period lasted for 74 h; the radiation period was 16 h PAR/UV-A per day, or with additional UV-B for 14 h per day. The effective quantum yield, generally lower in pre-Akinetes, was mostly reduced during the UV treatment, and recovery was significantly higher in young vegetative cells vs. pre-Akinetes during the experiment. Analysis of the deepoxidation state of the xanthophyll-cycle pigments revealed a statistically significant (p < 0.05) increase in Zygnema spp. C and S. The content of UV-absorbing phenolic compounds was significantly higher (p < 0.05) in young vegetative cells compared to pre-Akinetes. In young vegetative Zygnema sp. S, these phenolic compounds significantly increased (p < 0.05) upon PA and PAB. Transmission electron microscopy showed an intact ultrastructure with massive starch accumulations at the pyrenoids under PA and PAB. A possible increase in electron-dense bodies in PAB-treated cells and the occurrence of cubic membranes in the chloroplasts are likely protection strategies. Metabolite profiling by non-targeted RP-UHPLC-qToF-MS allowed a clear separation of the strains, but could not detect changes due to the PA and PAB treatments. Six hundred seventeen distinct molecular masses were detected, of which around 200 could be annotated from databases. These results indicate that young vegetative cells can adapt better to the experimental UV-B stress than pre-Akinetes.
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Nitrogen Limitation and Slow Drying Induce Desiccation Tolerance in Conjugating Green Algae (Zygnematophyceae, Streptophyta) from Polar Habitats
2016Co-Authors: Andreas HolzingerAbstract:Background: Filamentous Zygnematophyceae are typical components of algal mats in the polar hydro-terrestrial environment. Under field conditions, they form senescent vegetative cells, designated as pre-Akinetes, which are tolerant to desiccation and osmotic stress. Key Findings: Pre-Akinete formation and desiccation tolerance was investigated experimentally under monitored laboratory conditions in four strains of Arctic and Antarctic isolates with vegetative Zygnema sp. morphology. Phylogenetic analyses of rbcL sequences revealed one Arctic strain as genus Zygnemopsis, phylogenetically distant from the closely related Zygnema strains. Algae were cultivated in liquid or on solidified medium (9 weeks), supplemented with or lacking nitrogen. Nitrogen-free cultures (liquid as well as solidified) consisted of well-developed pre-Akinetes after this period. Desiccation experiments were performed at three different drying rates (rapid: 10 % relative humidity, slow: 86 % rh and very slow); viability, effective quantum yield of PS II, visual and ultrastructural changes were monitored. Recovery and viability of pre-Akinetes were clearly dependent on the drying rate: slower desiccation led to higher levels of survival. Pre-Akinetes survived rapid drying after acclimation by very slow desiccation. Conclusions: The formation of pre-Akinetes in polar Zygnema spp. and Zygnemopsis sp. is induced by nitrogen limitation. Pre-Akinetes, modified vegetative cells, rather than specialized stages of the life cycle, can be hardened by mild desiccatio
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nitrogen limitation and slow drying induce desiccation tolerance in conjugating green algae zygnematophyceae streptophyta from polar habitats
PLOS ONE, 2014Co-Authors: Martina Pichrtova, Jana Kulichová, Andreas HolzingerAbstract:Background Filamentous Zygnematophyceae are typical components of algal mats in the polar hydro-terrestrial environment. Under field conditions, they form senescent vegetative cells, designated as pre-Akinetes, which are tolerant to desiccation and osmotic stress. Key Findings Pre-Akinete formation and desiccation tolerance was investigated experimentally under monitored laboratory conditions in four strains of Arctic and Antarctic isolates with vegetative Zygnema sp. morphology. Phylogenetic analyses of rbcL sequences revealed one Arctic strain as genus Zygnemopsis, phylogenetically distant from the closely related Zygnema strains. Algae were cultivated in liquid or on solidified medium (9 weeks), supplemented with or lacking nitrogen. Nitrogen-free cultures (liquid as well as solidified) consisted of well-developed pre-Akinetes after this period. Desiccation experiments were performed at three different drying rates (rapid: 10% relative humidity, slow: 86% rh and very slow); viability, effective quantum yield of PS II, visual and ultrastructural changes were monitored. Recovery and viability of pre-Akinetes were clearly dependent on the drying rate: slower desiccation led to higher levels of survival. Pre-Akinetes survived rapid drying after acclimation by very slow desiccation. Conclusions The formation of pre-Akinetes in polar Zygnema spp. and Zygnemopsis sp. is induced by nitrogen limitation. Pre-Akinetes, modified vegetative cells, rather than specialized stages of the life cycle, can be hardened by mild desiccation stress to survive rapid drying. Naturally hardened pre-Akinetes play a key role in stress tolerance and dispersal under the extreme conditions of polar regions, where sexual reproduction and production of dormant stages is largely suppressed.
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Light micrographs of the strains pre-cultivated on agar medium for 9 weeks.
2014Co-Authors: Martina Pichrtova, Jana Kulichová, Andreas HolzingerAbstract:A–D: cultures grown on regular BBM medium (A BBM); E–H: cultures grown on BBM without nitrate (A BBM-N). The images were taken prior to the desiccation experiments; a Zygnema Akinete with a distinct brown mesospore is marked with an asterisk. Scale bars: 10 µm.
Assaf Sukenik - One of the best experts on this subject based on the ideXlab platform.
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Carbon assimilation and accumulation of cyanophycin during the development of dormant cells (Akinetes) in the cyanobacterium Aphanizomenon ovalisporum.
Frontiers in microbiology, 2015Co-Authors: Assaf Sukenik, Iris Maldener, Thomas Delhaye, Yehudit Viner-mozzini, Dotan Sela, Myriam BormansAbstract: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 with accumulation of cyanophycin; a copolymer of aspartate and arginine that forms storage granules. Cyanophycin accumulation is initiated in vegetative cells few days post exposure to Akinete inducing conditions. This early-accumulated cyanophycin pool in vegetative cells disappeared as a nearby cell differentiates to an Akinete and stores large pool of cyanophycin. During the Akinete maturation, the cyanophycin pool is further increased and comprise up to 2% of the Akinete volume. The cellular pattern of photosynthetic activity during Akinete formation was study by a nano-metric scale secondary ion mass spectrometry (NanoSIMS) analysis of 13C-enriched cultures. Quantitative estimation of carbon assimilation in vegetative cells and Akinetes (filament-attached and free) indicates that vegetative cells maintained their basal activity while differentiating Akinetes gradually reduced their activity. Mature free Akinetes practically lost their photosynthetic activity although small fraction of free Akinetes were still photosynthetically active. Additional 13C pulse chase experiments indicated rapid carbon turnover during Akinete formation and de novo synthesis of cyanophycin in vegetative cells 4 days post induction of Akinete differentiation.
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Potassium deficiency triggers the development of dormant cells (Akinetes) in Aphanizomenon ovalisporum (Nostocales, Cyanoprokaryota)(1).
Journal of phycology, 2013Co-Authors: Assaf Sukenik, Antonio Quesada, Yehudit Viner-mozzini, Ruth N. Kaplan-levy, Ora HadasAbstract:Akinetes are spore-like nonmotile 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. Various environmental factors were reported to trigger the differentiation of Akinetes including light intensity and quality, temperature, and nutrient deficiency. Here, we report that deprivation of potassium ion (K(+) ) triggers Akinete development in the cyanobacterium Aphanizomenon ovalisporum. Akinetes formation is initiated 3 d-7 d after an induction by K(+) depletion, followed by 2-3 weeks of a maturation process. Akinete formation occurs within a restricted matrix of environmental conditions such as temperature, light intensity or photon flux. Phosphate is essential for Akinete maturation and P-limitation restricts the number of mature Akinetes. DNA replication is essential for Akinete maturation and Akinete development is limited in the presence of Nalidixic acid. While our results unequivocally demonstrated the effect of K(+) deficiency on Akinete formation in laboratory cultures of A. ovalisporum, this trigger did not cause Cylindrospermopsis raciborskii to produce Akinetes. Anabaena crassa however, produced Akinetes upon potassium deficiency, but the highest Akinete concentration was achieved at conditions that supported vegetative growth. It is speculated that an unknown internal signal is associated with the cellular response to K(+) deficiency to induce the differentiation of a certain vegetative cell in a trichome into an Akinete. A universal stress protein that functions as mediator in K(+) deficiency signal transduction cascade, may communicate between the lack of K(+) and Akinete induction.
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massive multiplication of genome and ribosomes in dormant cells Akinetes of aphanizomenon ovalisporum cyanobacteria
The ISME Journal, 2012Co-Authors: Assaf Sukenik, Ruth N Kaplanlevy, Jessica Mark L Welch, Anton F PostAbstract:Akinetes are dormancy cells commonly found among filamentous cyanobacteria, many of which are toxic and/or nuisance, bloom-forming species. Development of Akinetes from vegetative cells is a process that involves morphological and biochemical modifications. Here, we applied a single-cell approach to quantify genome and ribosome content of Akinetes and vegetative cells in Aphanizomenon ovalisporum (Cyanobacteria). Vegetative cells of A. ovalisporum were naturally polyploid and contained, on average, eight genome copies per cell. However, the chromosomal content of Akinetes increased up to 450 copies, with an average value of 119 genome copies per Akinete, 15-fold higher than that in vegetative cells. On the basis of fluorescence in situ hybridization, with a probe targeting 16S rRNA, and detection with confocal laser scanning microscopy, we conclude that ribosomes accumulated in Akinetes to a higher level than that found in vegetative cells. We further present evidence that this massive accumulation of nucleic acids in Akinetes is likely supported by phosphate supplied from inorganic polyphosphate bodies that were abundantly present in vegetative cells, but notably absent from Akinetes. These results are interpreted in the context of cellular investments for proliferation following a long-term dormancy, as the high nucleic acid content would provide the basis for extended survival, rapid resumption of metabolic activity and cell division upon germination.
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photosynthetic characterization of developing and mature Akinetes of aphanizomenon ovalisporum cyanoprokaryota 1
Journal of Phycology, 2007Co-Authors: Assaf Sukenik, John Beardall, Ora HadasAbstract:Akinetes, differentiated resting cells produced by many species of filamentous, heterocystous cyanobacteria, enable the organism to survive adverse conditions, such as cold winters and dry seasons, and to maintain germination capabilities until the onset of suitable conditions for vegetative growth. Mature Akinetes maintain a limited level of metabolic activities, including photosynthesis. In the present study, we have characterized changes in the photosynthetic apparatus of vegetative cells and Akinetes of the cyanobacterium Aphanizomenon ovalisporum Forti (Nostocales) during their development and maturation. Photosynthetic variable fluorescence was measured by microscope-PAM (pulse-amplitude-modulated) fluorometry, and the fundamental composition of the photosynthetic apparatus was evaluated by fluorescence and immunological techniques. Vegetative cells and Akinetes from samples of Aphanizomenon trichomes from Akinete-induced cultures at various ages demonstrated a gradual reduction, with age, in the maximal photosynthetic quantum yield in both cell types. However, the maximal quantum yield of Akinetes declined slightly faster than that of their adjacent vegetative cells. Mature Akinetes isolated from 6- to 8-week-old Akinete-induced cultures maintained only residual photosynthetic activity, as indicated by very low values of maximal photosynthetic quantum yields. Based on 77 K fluorescence emission data and immunodetection of PSI and PSII polypeptides, we concluded that the ratio of PSI to PSII reaction centers in mature Akinetes is slightly higher than the ratio estimated for exponentially grown vegetative cells. Furthermore, the cellular abundance of these protein complexes substantially increased in Akinetes relative to exponentially grown vegetative cells, presumably due to considerable increase in the biovolume of Akinetes.
Antonio Quesada - One of the best experts on this subject based on the ideXlab platform.
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Overwintering populations of Anabaena, Aphanizomenon and Microcystis as potential inocula for summer blooms
Journal of Plankton Research, 2013Co-Authors: Samuel Cirés, Ramsy Agha, Lars Wörmer, Antonio QuesadaAbstract:Overwintering cyanobacterial populations of Nostocales and Microcystis were investigated in six freshwater reservoirs in Northwestern Spain during two consecutive winters. Surface sediments hosted 10–10 Akinetes mL and 10–10 Microcystis colonies mL. Sediments from deeper areas close to dam accumulated 2-fold (Microcystis) and 11-fold (Akinetes) greater concentrations than those at the shallower upstream areas. Anabaena spp. and Microcystis aeruginosa dominated the sediment pool, with minor amounts of Akinetes of Aphanizomenon (Aph. flos-aquae, Aph. gracile) and benthic Nostocales (Cylindrospermum, Nostoc and Trichormus). Our study confirms the dual benthic-pelagic overwintering of Anabaena, Aphanizomenon and Microcystis, found in the pelagial at 7.5–9.88C. This study also provides an insight into the little known annual cycle of potential cyanotoxin-producers Aph. gracile and Anabaena circinalis. Our estimates show that: (i) only a small fraction (,1%) of the sediment pool of Akinetes and Microcystis was resupended in the bottom water during winter which, however, may be sufficient inocula to build up the summer maxima under realistic in situ growth rates; and (ii) the time required for the development of summer populations is mainly driven by growth rates, and therefore by the environmental conditions faced by the inoculum, with a lower influence (although greater for Microcystis than for Nostocales) of the inoculum size.
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Potassium deficiency triggers the development of dormant cells (Akinetes) in Aphanizomenon ovalisporum (Nostocales, Cyanoprokaryota)(1).
Journal of phycology, 2013Co-Authors: Assaf Sukenik, Antonio Quesada, Yehudit Viner-mozzini, Ruth N. Kaplan-levy, Ora HadasAbstract:Akinetes are spore-like nonmotile 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. Various environmental factors were reported to trigger the differentiation of Akinetes including light intensity and quality, temperature, and nutrient deficiency. Here, we report that deprivation of potassium ion (K(+) ) triggers Akinete development in the cyanobacterium Aphanizomenon ovalisporum. Akinetes formation is initiated 3 d-7 d after an induction by K(+) depletion, followed by 2-3 weeks of a maturation process. Akinete formation occurs within a restricted matrix of environmental conditions such as temperature, light intensity or photon flux. Phosphate is essential for Akinete maturation and P-limitation restricts the number of mature Akinetes. DNA replication is essential for Akinete maturation and Akinete development is limited in the presence of Nalidixic acid. While our results unequivocally demonstrated the effect of K(+) deficiency on Akinete formation in laboratory cultures of A. ovalisporum, this trigger did not cause Cylindrospermopsis raciborskii to produce Akinetes. Anabaena crassa however, produced Akinetes upon potassium deficiency, but the highest Akinete concentration was achieved at conditions that supported vegetative growth. It is speculated that an unknown internal signal is associated with the cellular response to K(+) deficiency to induce the differentiation of a certain vegetative cell in a trichome into an Akinete. A universal stress protein that functions as mediator in K(+) deficiency signal transduction cascade, may communicate between the lack of K(+) and Akinete induction.
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temperature dependent dispersal strategies of aphanizomenon ovalisporum nostocales cyanobacteria implications for the annual life cycle
Microbial Ecology, 2013Co-Authors: Samuel Cirés, Lars Wörmer, Claudia Wiedner, Antonio QuesadaAbstract:Aphanizomenon ovalisporum is a planktonic nostocalean cyanobacterium with increasing research interest due to its ability to produce the potent cytotoxin cylindrospermopsin and its potential invasiveness under the global warming scenario. The present study provides novel data on the potential dispersal strategies of A. ovalisporum by analyzing the influence of temperature (10–40 °C) on Akinete differentiation and cell morphometry in cultures of A. ovalisporum UAM 290 isolated from a Spanish pond. Our results confirmed a temperature-dependent Akinete differentiation, with the maximum Akinete production reached at 20 °C (15 % of the cells), a low basal production at 25–30 °C (<0.4 % of the cells) and no detectable production at 35 °C. Furthermore, we reported the fragmentation of A. ovalisporum filaments at temperatures of 25 °C and above. Additionally, we observed that the morphology of vegetative cells varied under different temperature scenarios. Indeed, a strong negative correlation was found between temperature and the width, length and biovolume of vegetative cells, whereas Akinete dimensions remained stable along the temperature gradient. Therefore, linear regressions between temperature and the cell size parameters are herein presented aiming to facilitate the identification of A. ovalisporum in the field throughout the course of the year. This is the first study evidencing that Akinete production is triggered by temperatures between 20 and 25 °C in A. ovalisporum and reporting the existence of filament fragmentation as a potential dispersal strategy of this species. The importance of these findings for understanding the annual life cycle and invasive potential of A. ovalisporum is further discussed herein.
Martina Pichrtova - One of the best experts on this subject based on the ideXlab platform.
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arctic antarctic and temperate green algae zygnema spp under uv b stress vegetative cells perform better than pre Akinetes
Protoplasma, 2018Co-Authors: Andreas Holzinger, Siegfried Aigner, Kateřina Trumhova, Philippe Schmittkopplin, Andreas Albert, Martina PichrtovaAbstract:Species of Zygnema form macroscopically visible mats in polar and temperate terrestrial habitats, where they are exposed to environmental stresses. Three previously characterized isolates (Arctic Zygnema sp. B, Antarctic Zygnema sp. C, and temperate Zygnema sp. S) were tested for their tolerance to experimental UV radiation. Samples of young vegetative cells (1 month old) and pre-Akinetes (6 months old) were exposed to photosynthetically active radiation (PAR, 400–700 nm, 400 μmol photons m−2 s−1) in combination with experimental UV-A (315–400 nm, 5.7 W m−2, no UV-B), designated as PA, or UV-A (10.1 W m−2) + UV-B (280–315 nm, 1.0 W m−2), designated as PAB. The experimental period lasted for 74 h; the radiation period was 16 h PAR/UV-A per day, or with additional UV-B for 14 h per day. The effective quantum yield, generally lower in pre-Akinetes, was mostly reduced during the UV treatment, and recovery was significantly higher in young vegetative cells vs. pre-Akinetes during the experiment. Analysis of the deepoxidation state of the xanthophyll-cycle pigments revealed a statistically significant (p < 0.05) increase in Zygnema spp. C and S. The content of UV-absorbing phenolic compounds was significantly higher (p < 0.05) in young vegetative cells compared to pre-Akinetes. In young vegetative Zygnema sp. S, these phenolic compounds significantly increased (p < 0.05) upon PA and PAB. Transmission electron microscopy showed an intact ultrastructure with massive starch accumulations at the pyrenoids under PA and PAB. A possible increase in electron-dense bodies in PAB-treated cells and the occurrence of cubic membranes in the chloroplasts are likely protection strategies. Metabolite profiling by non-targeted RP-UHPLC-qToF-MS allowed a clear separation of the strains, but could not detect changes due to the PA and PAB treatments. Six hundred seventeen distinct molecular masses were detected, of which around 200 could be annotated from databases. These results indicate that young vegetative cells can adapt better to the experimental UV-B stress than pre-Akinetes.
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nitrogen limitation and slow drying induce desiccation tolerance in conjugating green algae zygnematophyceae streptophyta from polar habitats
PLOS ONE, 2014Co-Authors: Martina Pichrtova, Jana Kulichová, Andreas HolzingerAbstract:Background Filamentous Zygnematophyceae are typical components of algal mats in the polar hydro-terrestrial environment. Under field conditions, they form senescent vegetative cells, designated as pre-Akinetes, which are tolerant to desiccation and osmotic stress. Key Findings Pre-Akinete formation and desiccation tolerance was investigated experimentally under monitored laboratory conditions in four strains of Arctic and Antarctic isolates with vegetative Zygnema sp. morphology. Phylogenetic analyses of rbcL sequences revealed one Arctic strain as genus Zygnemopsis, phylogenetically distant from the closely related Zygnema strains. Algae were cultivated in liquid or on solidified medium (9 weeks), supplemented with or lacking nitrogen. Nitrogen-free cultures (liquid as well as solidified) consisted of well-developed pre-Akinetes after this period. Desiccation experiments were performed at three different drying rates (rapid: 10% relative humidity, slow: 86% rh and very slow); viability, effective quantum yield of PS II, visual and ultrastructural changes were monitored. Recovery and viability of pre-Akinetes were clearly dependent on the drying rate: slower desiccation led to higher levels of survival. Pre-Akinetes survived rapid drying after acclimation by very slow desiccation. Conclusions The formation of pre-Akinetes in polar Zygnema spp. and Zygnemopsis sp. is induced by nitrogen limitation. Pre-Akinetes, modified vegetative cells, rather than specialized stages of the life cycle, can be hardened by mild desiccation stress to survive rapid drying. Naturally hardened pre-Akinetes play a key role in stress tolerance and dispersal under the extreme conditions of polar regions, where sexual reproduction and production of dormant stages is largely suppressed.
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Light micrographs of the strains pre-cultivated on agar medium for 9 weeks.
2014Co-Authors: Martina Pichrtova, Jana Kulichová, Andreas HolzingerAbstract:A–D: cultures grown on regular BBM medium (A BBM); E–H: cultures grown on BBM without nitrate (A BBM-N). The images were taken prior to the desiccation experiments; a Zygnema Akinete with a distinct brown mesospore is marked with an asterisk. Scale bars: 10 µm.
John C Meeks - One of the best experts on this subject based on the ideXlab platform.
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global gene expression patterns of nostoc punctiforme in steady state dinitrogen grown heterocyst containing cultures and at single time points during the differentiation of Akinetes and hormogonia
Journal of Bacteriology, 2007Co-Authors: Elsie L Campbell, Michael L Summers, Harry D Christman, Miriam E Martin, John C MeeksAbstract:The vegetative cells of the filamentous cyanobacterium Nostoc punctiforme can differentiate into three mutually exclusive cell types: nitrogen-fixing heterocysts, spore-like Akinetes, and motile hormogomium filaments. A DNA microarray consisting of 6,893 N. punctiforme genes was used to identify the global transcription patterns at single time points in the three developmental states, compared to those in ammonium-grown time zero cultures. Analysis of ammonium-grown cultures yielded a transcriptome of 2,935 genes, which is nearly twice the size of a soluble proteome. The NH4+-grown transcriptome was enriched in genes encoding core metabolic functions. A steady-state N2-grown (heterocyst-containing) culture showed differential transcription of 495 genes, 373 of which were up-regulated. The majority of the up-regulated genes were predicted from studies of heterocyst differentiation and N2 fixation; other genes are candidates for more detailed genetic analysis. Three days into the developmental process, Akinetes showed a similar number of differentially expressed genes (497 genes), which were equally up- and down-regulated. The down-regulated genes were enriched in core metabolic functions, consistent with entry into a nongrowth state. There were relatively few adaptive genes up-regulated in 3-day Akinetes, and there was little overlap with putative heterocyst developmental genes. There were 1,827 differentially transcribed genes in 24-h hormogonia, which was nearly fivefold greater than the number in Akinete-forming or N2-fixing cultures. The majority of the up-regulated adaptive genes were genes encoding proteins for signal transduction and transcriptional regulation, which is characteristic of a motile filament that is poised to sense and respond to the environment. The greatest fraction of the 883 down-regulated genes was involved in core metabolism, also consistent with entry into a nongrowth state. The differentiation of heterocysts (steady state, N2 grown), Akinetes, and hormogonia appears to involve the up-regulation of genes distinct for each state.
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Global Gene Expression Patterns of Nostoc punctiforme in Steady-State Dinitrogen-Grown Heterocyst-Containing Cultures and at Single Time Points during the Differentiation of Akinetes and Hormogonia � †
2007Co-Authors: Elsie L Campbell, Michael L Summers, Miriam E Martin, Harry Christman, John C MeeksAbstract:The vegetative cells of the filamentous cyanobacterium Nostoc punctiforme can differentiate into three mutually exclusive cell types: nitrogen-fixing heterocysts, spore-like Akinetes, and motile hormogomium filaments. A DNA microarray consisting of 6,893 N. punctiforme genes was used to identify the global transcription patterns at single time points in the three developmental states, compared to those in ammonium-grown time zero cultures. Analysis of ammonium-grown cultures yielded a transcriptome of 2,935 genes, which is nearly twice the size of a soluble proteome. The NH4-grown transcriptome was enriched in genes encoding core metabolic functions. A steady-state N2-grown (heterocyst-containing) culture showed differential transcription of 495 genes, 373 of which were up-regulated. The majority of the up-regulated genes were predicted from studies of heterocyst differentiation and N2 fixation; other genes are candidates for more detailed genetic analysis. Three days into the developmental process, Akinetes showed a similar number of differentially expressed genes (497 genes), which were equally up- and down-regulated. The down-regulated genes were enriched in core metabolic functions, consistent with entry into a nongrowth state. There were relatively few adaptive genes up-regulated in 3-day Akinetes, and there was little overlap with putative heterocyst developmental genes. There were 1,827 differentially transcribed genes in 24-h hormogonia, which was nearly fivefold greater than the number in Akinete-forming or N2-fixing cultures. The majority of the up-regulated adaptiv