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Simple Summary: This review highlights six genetic collections of algae, cyanobacteria, and plant materials maintained at the Institute of Plant Physiology of the Russian Academy of Sciences (IPPRAS) since the 1950–1970s using in vitro and cryopreservation techniques. The in vitro collections conserve over 430 strains of algae and cyanobacteria, more than 200 transgenic and non-transgenic potato clones, 117 cell cultures, and 50 strains of hairy and adventitious root cultures of medicinal and model plant species. The IPPRAS cryobank of plant genetic resources preserves in vitro-derived germplasm and seeds of wild and cultivated plants from 457 species and 74 families. This review discusses the collections' major activities and their extensive use in research, biotechnological interventions, commercial application, and biodiversity conservation. We also emphasize the role of in vitro collections as a genetic basis for green biotechnologies. Ex situ collections of algae, cyanobacteria, and plant materials (cell cultures, hairy and adventitious root cultures, shoots, etc.) maintained in vitro or in liquid nitrogen (−196 °C, LN) are valuable sources of strains with unique ecological and biotechnological traits. Such collections play a vital role in bioresource conservation, science, and industry development but are rarely covered in publications. Here, we provide an overview of five genetic collections maintained at the Institute of Plant Physiology of the Russian Academy of Sciences (IPPRAS) since the 1950–1970s using in vitro and cryopreservation approaches. These collections represent different levels of plant organization, from individual cells (cell culture collection) to organs (hairy and adventitious root cultures, shoot apices) to in vitro plants. The total collection holdings comprise more than 430 strains of algae and cyanobacteria, over 200 potato clones, 117 cell cultures, and 50 strains of hairy and adventitious root cultures of medicinal and model plant species. The IPPRAS plant cryobank preserves in LN over 1000 specimens of in vitro cultures and seeds of wild and cultivated plants belonging to 457 species and 74 families. Several algae and plant cell culture strains have been adapted for cultivation in bioreactors from laboratory (5–20-L) to pilot (75-L) to semi-industrial (150–630-L) scale for the production of biomass with high nutritive or pharmacological value. Some of the strains with proven biological activities are currently used to produce cosmetics and food supplements. Here, we provide an overview of the current collections' composition and major activities, their use in research, biotechnology, and commercial application. We also highlight the most interesting studies performed with collection strains and discuss strategies for the collections' future development and exploitation in view of current trends in biotechnology and genetic resources conservation. [ABSTRACT FROM AUTHOR]

Flat-panel photobioreactors are effective systems for microalgae cultivation. This paper presents the growth characteristics of the microalgae Chlorella sorokiniana IPPAS C-1 as a result of three-stage scale-up cultivation in a specially designed cultivation system. First, C. sorokiniana was grown aseptically in 250 mL glass vessels; then, it was diluted and inoculated into a 5-liter flat-panel horizontal photobioreactor; and, at the last stage, the culture was diluted and inoculated into a 70-liter flat-panel vertical photobioreactor. In the presented cycle, the cultured biomass increased by 326 times in 13 days (from 0.6 to 195.6 g dw), with a final biomass concentration of 2.8 g dw L−1. The modes of semi-continuous cultivation were considered. The biomass harvest and dilution of the suspension were carried out either every day or every 3–4 days. For C. sorokiniana IPPAS C-1, a conversion coefficient of optical density values to dry biomass (g L−1) was refined through a factor of 0.33. The key parameters of the photobioreactors tested in this work are discussed. [ABSTRACT FROM AUTHOR]

Several forms of EcaA protein, correspondent to the extracellular α-class carbonic anhydrase (CA) of cyanobacterium Crocosphaera subtropica ATCC 51142 were expressed in Escherichia coli. The recombinant proteins with no leader peptide (EcaA and its fusion with thioredoxin or glutathione S-transferase) were allocated inside cells in a full-length form; these cells did not display any extracellular CA activity. Soluble proteins (including that of periplasmic space) of E. coli cells that expressed both ЕсаА equipped with its native leader peptide (L -EcaA) as well as L -EcaA fused with thioredoxin or glutathione S-transferase at N -terminus, mainly contained the processed EcaA. The appearance of mature ЕсаА in outer layers of E. coli cells expressed leader peptide-containing forms of recombinant proteins, has been directly confirmed by immunofluorescent microscopy. Those cells also displayed high extracellular CA activity. In addition, the mature EcaA protein was detected in the culture medium. This suggests that cyanobacterial signal peptide is recognized by the secretory machinery and by the leader peptidase of E. coli even as a part of a fusion protein. The efficiency of EcaA leader peptide was comparable to that of PelB and TorA signal peptides, commonly used for biotechnological production of extracellular recombinant proteins in E. coli. • EcaA is the extracellular carbonic anhydrase of C. subtropica ATCC 51142. • Leader peptide of EcaA ensures efficient secretion of recombinant proteins in E. coli. • Leader peptide of EcaA efficiently functions even as a part of a fusion protein. • The efficiency of EcaA leader peptide is comparable to that of PelB and TorA leaders. [ABSTRACT FROM AUTHOR]

Filamentous cyanobacteria belonging to the 'marine Geitlerinema ' cluster are spread worldwide in saline environments and considered to play an important ecological role. However, the taxonomy of this group remains unclear. Here, we analyzed the phylogeny, ecology and biogeography of the 'marine Geitlerinema ' cluster representatives and revealed two subclusters: (1) an 'oceanic' subcluster containing PCC7105 clade and black band disease (BBD) clade with free-living and pathogenic strains distributed in Atlantic, Indian and Pacific Ocean-related localities, and (2) a Sodalinema subcluster containing free-living strains from marine, hypersaline, saline-alkaline and soda lake habitats from the Eurasian and African continents. Polyphasic analysis using genetic and phenotypic criteria demonstrated that these two groups represent separate genera. Representatives of Sodalinema subcluster were phylogenetically attributed to the genus Sodalinema. Our data expand the ecological and geographical distribution of this genus. We emended the description of the genus Sodalinema and proposed three new species differing in phylogenetic, geographic and ecological criteria: Sodalinema orleanskyi sp. nov. Sodalinema gerasimenkoae sp. nov. and Sodalinema stali sp. nov. Additionally, a new genus and species Baaleninema simplex gen. et sp. nov. was discribed within the PCC7105 clade. By this, we put in order the current confusion of the 'marine Geitlerinema ' group and highlight its ecological diversity. [ABSTRACT FROM AUTHOR]

• Salt stress inhibited growth of Vischeria punctata. • Salt-stressed cells were bigger, had larger chloroplasts and many mitochondria. • Salt stress resulted in a disordered thylakoid arrangement and D1 protein depletion. • Salt-stressed cells had more proteins. • Lipids of salt-stressed cells had higher proportion of eicosapentaenoic acid. The strain IPPAS H-242 is an eustigmatophycean alga with good growth characteristics and high content of the long chain polyunsaturated eicosapentaenoic fatty acid (EPA) – a very-long-chain fatty acid with high nutraceutical value. In this study, based on 18S rRNA gene and ITS1–5.8S–ITS2 sequences the strain IPPAS H-242 was identified as an authentic strain of Vischeria punctata. The effect of salt stress (0.5 M NaCl) on growth, cell morphology, ultrastructure, and biochemical composition with the emphasis on the fatty acid (FA) profile was investigated in batch cultures. Under salt stress, biomass accumulation and cell division were severely inhibited; cells were bigger, with higher chloroplast volume and numerous mitochondria, they had more proteins (73 % from the initial concentration as compared to 23 % in control) and their lipids had higher EPA proportion (13.6 % of total FA as compared to 6.4 % of total FA in control). In salt-stressed cells, thylakoid organization and photosynthetic activity were impaired, and D1 protein content decreased to trace amounts. In spite of an increase in EPA proportion in total FA, salt stress causes a decrease in total EPA productivity (49 mg/L as compared to 130 mg/L in control). [ABSTRACT FROM AUTHOR]

The microalgae Vischeria sp. IPPAS C-70 produces eicosapentaenoic acid. Several stresses cause the formation of fatty acid peaks that resemble hexadecadienoic acids. We used the integrated technique including TLC, HPLC, and GC–MS to search and determine these fatty acids. Double bond positioning in these fatty acids indicated that they were conjugated dienes and allenes. We identified and described natural nine isomers of C16 polyunsaturated fatty acids, including common methylene-interrupted dienes (Δ6,9-16:2, Δ7,10-16:2, Δ9,12-16:2), and unusual conjugated dienes (Δ6,8-, Δ7,9-, Δ8,10-, Δ9,11-, and Δ10,12-16:2), as well as allenic diene (Δ9,10-16:2). We hypothesize that the formation of conjugated dienes and allenes among fatty acids is the result of oxidative stress caused by H2O2. Hydrogen peroxide also caused an increase in saturated at the expense of unsaturated fatty acids, suggesting inhibition either fatty acid desaturases activities or the corresponding gene expression. [ABSTRACT FROM AUTHOR]

In this study, a simple and rapid DAPI-based protocol was developed and optimized to visualize polyphosphates (polyPs) in the cyanobacterium Synechocystis sp. PCC 6803. The optimum dye concentration and incubation time were determined, and formaldehyde fixation was shown to significantly improve polyP detection in Synechocystis cells. Using the developed protocol, for the first time, it was shown that 80% of Synechocystis cells under phosphate overplus were able to accumulate phosphorus as polyP 3 min after the addition of K2HPO4. After 1 h, the number of cells with polyP began to decrease, and after 24 h, polyP granules were detected in only 30% of the cells. Thus, the Synechocystis cells appeared to be heterogeneous in their ability to accumulate and mobilize polyP. Like other photosynthetic organisms, Synechocystis synthesized less polyP in the dark than in the light. The accumulation of polyP was not inhibited under conditions of cold and heat stresses, and some cells were even able to synthesize polyP at a temperature of approximately 0 °C. [ABSTRACT FROM AUTHOR]

Here, for the first time, we report the presence of highly active extracellular carbonic anhydrase (CA) of α-class in cyanobacterial cells. The enzyme activity was confirmed both in vivo in intact cells and in vitro , using the recombinant protein. CA activity in intact cells of Cyanothece sp. ATCC 51142 reached ∼0.6 Wilbur–Anderson units (WAU) per 1 mg of total cell protein, and it was inhibited by a specific CAs inhibitor, ethoxyzolamide. The genes cce_4328 (ecaA) and cce_0871 (ecaB), encoding two potential extracellular CAs of Cyanothece have been cloned, and the corresponding proteins EcaA and EcaB, representing CAs of α- and β-class, respectively, have been heterologously expressed in Escherichia coli. High specific activity (∼1.1 × 104 WAU per 1 mg of target protein) was detected for the recombinant EcaA only. The presence of EcaA in the outer cellular layers of Cyanothece was confirmed by immunological analysis with antibodies raised against the recombinant protein. The absence of redox regulation of EcaA activity indicates that this protein does not possess a disulfide bond essential for some α-class CAs. The content and activity of EcaA in a fraction of periplasmic proteins was higher in Cyanothece cells grown at ambient concentration of CO 2 (0.04%) compared to those grown at an elevated CO 2 concentration (1.7%). At the same time, the level of ecaA gene mRNA varied insignificantly in response to changes in CO 2 supply. Our results indicate that EcaA is responsible for CA activity of intact Cyanothece cells and point to its possible physiological role under low-CO 2 conditions. • Cyanothece sp. ATCC 51142 intact cells possess carbonic anhydrase activity. • This activity is insured by EcaA protein located in cell envelopes of Cyanothece. • Content and activity of EcaA in periplasm is higher at low-CO 2 conditions. • Physiological significance of EcaA under low-CO 2 conditions is assumed. [ABSTRACT FROM AUTHOR]

A cyanobacterial strain from Lake Shar-Nuur, a freshwater lake in Mongolia, was isolated and characterized by a polyphasic approach. According to the 16S ribosomal RNA gene sequence, this strain (IPPAS B-1220) belongs to a newly described genus Desertifilum. In general, strains of Desertifilum maintain their genetic stability, as seen from the analysis of the 16S rRNA gene and 16S-23S rRNA internal transcribed spacer sequences from strains collected at distant locations. The newly discovered strain is characterized by an unusual fatty acid composition (16:1Δ7 and 16:2Δ7,10). Analysis of its draft genomic sequence reveals the presence of six genes for the acyl-lipid desaturases: two Δ9-desaturases, desC1 and desC2; two Δ12-desaturases, desA1 and desA2; one desaturase of unknown specificity, desX; and one gene for the bacillary-type desaturase, desG, which supposedly encodes an ω9-desaturase. A scheme for a fatty acid desaturation pathway that describes the biosynthesis of 16:1Δ7 and 16:2Δ7,10 fatty acids in Desertifilum is proposed. [ABSTRACT FROM AUTHOR]

Background Cold stress strongly induces the expression of ~ 100 genes in cyanobacteria. Some of these genes are necessary to protect cellular functions by adjustment of membranes, as well as transcriptional and translational machineries. About a half of cold-induced genes are not functionally characterized. A part of cold-induced genes is under control of a two-component regulatory system, consisting of histidine kinase Hik33 and response regulator Rre26. The mechanism(s) that control another part of cold-inducible genes are still unknown. Scope of review The aim of this review is to summarise the latest findings in cyanobacterial cold-stress responses including transcriptomics, cold sensing, and molecular triggers. Major conclusions A feedback loop between the membrane fluidity and transcription of genes for fatty acid desaturases operates via the transmembrane red-light-activated cold sensor Hik33, which perceives cold-induced membrane rigidification as a change in its thickness. The cold-induced kinase activity of Hik33 is facilitated by interaction with a small protein, Ssl3451 – the third contributor to a canonical two-component regulatory system, which may explain the ability of some cyanobacterial histidine kinases to interact with different response regulators under different stress conditions. Other regulatory systems that control cold-stress responses operate via Ser/Thr protein kinase, SpkE, and via temperature-dependent changes in DNA supercoiling. Transcriptomic analysis shows that universal triggers of stress responses are reactive oxygen species and changes in redox status of plastoquinone pool. General significance Deeper understanding of molecular mechanisms of temperature sensing and regulation of cold-stress responses in photosynthetic cells provide a background for generation of cold-resistant crops. [ABSTRACT FROM AUTHOR]

Cyanobacterial aquaporins play an important role in the regulation of various physiological functions: cell volume control, osmotic stress responses, gas exchange. We employed the AqpZ-deficient mutant of Synechocystis to study the role of aquaporins in responses to salt (NaCl) and high light stress. Electron microscopy and paramagnetic resonance revealed that AqpZ-deficient cells are unable to efficiently regulate the cytoplasmic volume under salt stress. Both photosystems (PSII and, especially, PSI) of these cells are more sensitive to NaCl and to high light. Thus, AqpZ of Synechocystis participates in regulation of the photosynthetic activity of PSI and PSII under salt and high-light stress. Our results demonstrate that AqpZ might be necessary for the repair of PSII and PSI after photodamage. [ABSTRACT FROM AUTHOR]

Synechocystis sp. PCC 6803 is a widely used model cyanobacterium for studying responses and acclimation to different abiotic stresses. Changes in transcriptome, proteome, lipidome, and photosynthesis in response to short term heat stress are well studied in this organism, and histidine kinase 34 (Hik34) is shown to play an important role in mediating such response. Corresponding data on long term responses, however, are fragmentary and vary depending on parameters of experiments and methods of data collection, and thus are hard to compare. In order to elucidate how the early stress responses help cells to sustain long-term heat stress, as well as the role of Hik34 in prolonged acclimation, we examined the resistance to long-term heat stress of wild-type and ΔHik34 mutant of Synechocystis. In this work, we were able to precisely control the long term experimental conditions by cultivating Synechocystis in automated photobioreactors, measuring selected physiological parameters within a time range of minutes. In addition, morphological and ultrastructural changes in cells were analyzed and western blotting of individual proteins was used to study the heat stress-affected protein expression. We have shown that the majority of wild type cell population was able to recover after 24 h of cultivation at 44 °C. In contrast, while ΔHik34 mutant cells were resistant to heat stress within its first hours, they could not recover after 24 h long high temperature treatment. We demonstrated that the early induction of HspA expression and maintenance of high amount of other HSPs throughout the heat incubation is critical for successful adaptation to long-term stress. In addition, it appears that histidine kinase Hik34 is an essential component for the long term high temperature resistance. [ABSTRACT FROM AUTHOR]

We characterized the photoautotrophic growth of glucose-tolerant Synechocystis sp. PCC 6803 in a flat-panel photobioreactor running on a semicontinuous regime under various lights, temperatures, and influx carbon dioxide concentrations. The maximum reached growth rate was 0.135 h−1, which corresponds to a doubling time of 5.13 h-a growth speed never reported for Synechocystis before. Saturating red light intensity for the strain was 220-360 μmol(photons) m−2 s−1, and we did not observe any photoinhibition up to 660 μmol(photons) m−2 s−1. Synechocystis was able to grow under red light only; however, photons of wavelengths 405-585 and 670-700 nm further improved its growth. Optimal growth temperature was 35°C. Below 32°C, the growth rates decreased linearly with temperature coefficient ( Q10) 1.70. Semicontinuous cultivation is known to be efficient for growth characterization and optimization. However, the assumption of correct growth rates calculation-culture exponential growth-is often not fulfilled. The semicontinuous setup in this study was operated as a turbidostat. Accurate online OD measurements with high time-resolution allowed fast and reliable growth rates determination. Repeating diluting frequencies (up to 18 dilutions per day) were essential for rapid growth stability evaluation. The presented setup provides improvement to previously published semicontinuous characterization strategies by decreasing experimental time requirements and maintaining the culture in exponential growth phase throughout the entire characterization procedure. [ABSTRACT FROM AUTHOR]

The unicellular cyanobacterium Cyanothece sp. American Type Culture Collection (ATCC) 51142 is capable of performing oxygenic photosynthesis during the day and microoxic nitrogen fixation at night. These mutually exclusive processes are possible only by temporal separation by circadian clock or another cellular program. We report identification of a temperature-dependent ultradian metabolic rhythm that controls the alternating oxygenic and microoxic processes of Cyanothece sp. ATCC 51142 under continuous high irradiance and in high CO2 concentration. During the oxygenic photosynthesis phase, nitrate deficiency limited protein synthesis and CO2 assimilation was directed toward glycogen synthesis. The carbohydrate accumulation reduced overexcitation of the photosynthetic reactions until a respiration burst initiated a transition to microoxic N2 fixation. In contrast to the circadian clock, this ultradian period is strongly temperature-dependent: 17 h at 27 °C, which continuously decreased to 10 h at 39 °C. The cycle was expressed by an oscillatory modulation of net O2 evolution, CO2 uptake, pH, fluorescence emission, glycogen content, cell division, and culture optical density. The corresponding ultradian modulation was also observed in the transcription of nitrogenase-related nifB and nifH genes and in nitrogenase activities. We propose that the control by the newly identified metabolic cycle adds another rhythmic component to the circadian clock that reflects the true metabolic state depending on the actual temperature, irradiance, and CO2 availability. [ABSTRACT FROM AUTHOR]

Abstract: The unicellular, nitrogen fixing cyanobacterium Cyanothece sp. ATCC 51142 is of a remarkable potential for production of third-generation biofuels. As the biotechnological potential of Cyanothece 51142 varies with the time of the day, we argue that it will, similarly, depend on the phase of the culture growth. Here, we study the batch culture dynamics to discover the dominant constraints in the individual growth phases and identify potential for inducing or delaying transitions between culture growth phases in Cyanothece 51142. We found that specific growth rate in the exponential phase of the culture is much less dependent on incident irradiance than the photosynthetic activity. We propose that surplus electrons that are released by water splitting are used in futile processes providing photoprotection additional to non-photochemical quenching. We confirm that the transition from exponential to linear phase is caused by a light limitation and the transition from linear to stationary phase by nitrogen limitation. We observe spontaneous diurnal metabolic oscillations in stationary phase culture that are synchronized over the entire culture without an external clue. We tentatively propose that the self-synchronization of the metabolic oscillations is due to a cell-to-cell communication of the cyanobacteria that is necessary for nitrogenase activity in nitrate depleted medium. [Copyright &y& Elsevier]

Abstract: The distribution of the luminal carbonic anhydrase Cah3 associated with thylakoid membranes in the chloroplast and pyrenoid was studied in wild-type cells of Chlamydomonas reinhardtii and in its cia3 mutant deficient in the activity of the Cah3 protein. In addition, the effect of CO2 concentration on fatty acid composition of photosynthetic membranes was examined in wild-type cells and in the cia3 mutant. In the cia3 mutant, the rate of growth was lower as compared to wild-type, especially in the cells grown at 0.03% CO2. This might indicate a participation of thylakoid Cah3 in the CO2-concentrating mechanism (CCM) of chloroplast and reflect the dysfunction of the CCM in the cia3 mutant. In both strains, a decrease in the CO2 concentration from 2% to 0.03% caused an increase in the content of polyunsaturated fatty acids in membrane lipids. At the same time, in the cia3 mutant, the increase in the majority of polyunsaturated fatty acids was less pronounced as compared to wild-type cells, whereas the amount of 16:4ω3 did not increase at all. Immunoelectron microscopy demonstrated that luminal Cah3 is mostly located in the thylakoid membranes that pass through the pyrenoid. In the cells of CCM-mutant, cia3, the Cah3 protein was much less abundant, and it was evenly distributed throughout the pyrenoid matrix. The results support our hypothesis that CO2 might be generated from HCO3 − by Cah3 in the thylakoid lumen with the following CO2 diffusion into the pyrenoid, where the CO2 fixing Rubisco is located. This ensures the maintenance of active photosynthesis under CO2-limiting conditions, and, as a result, the active growth of cells. The relationships between the induction of CCM and restructuring of the photosynthetic membranes, as well as the involvement of the Cah3 of the pyrenoid in these events, are discussed. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial. [Copyright &y& Elsevier]

Abstract: The gene for β-class carbonic anhydrase (CA), which was designated as cahB1, was cloned from the genomic library of the alkaliphilic cyanobacterium Microcoleus chthonoplastes. The product of the cahB1 gene was expressed in Escherichia coli. The protein revealed high specific activity of CA, which was inhibited with ethoxyzolamide. The maximum activity of the recombinant CA was detected at alkaline pH (∼9.0) and its minimum – at neutral pH (∼7.0). Western blotting analysis with the antibodies raised against the recombinant CahB1 protein revealed its localization in cell envelopes of M. chthonoplastes. Immunocytochemical localization of the CahB1 in cells confirmed its extracellular location. The newly characterized CahB1 of Microcoleus was similar in amino acid and nucleotide sequences to well known β-CAs of Synechococcus sp. PCC 7942 (IcfA) and Synechocystis sp. PCC 6803 (CcaA), although those CAs were attributed to the carboxysomal shells of cyanobacteria. Previously we have reported β-class CA which was associated with PS II of alkaliphilic cyanobacteria. Here we first report extracellular localization of β-class CA and provide a scheme for its possible involvement in the maintenance of a balance between external sources of inorganic carbon and photosynthesis in extreme environments of soda lakes. [Copyright &y& Elsevier]

Microalgae are increasingly being used for capturing carbon dioxide and converting it into valuable metabolites and biologically active compounds on an industrial scale. The efficient production of microalgae biomass requires the optimization of resources, including CO2. Here, we estimated the productivity of Chlorella sorokiniana IPPAS C-1 depending on CO2 concentrations and the ventilation coefficient of the gas-air mixture (GAM) in flat-panel photobioreactors (FP-PBRs) at laboratory (5 L) and pilot (18 L) scales. For the laboratory scale, the PBRs operated at 900 µmol quanta m−2 s−1 and 35.5 ± 0.5 °C; the optimal CO2 flow rate was estimated at 3 mL CO2 per 1 L of suspension per minute, which corresponds to 1.5% CO2 in the GAM and an aeration rate of 0.2 vvm. These parameters, being scaled up within the pilot PBRs, resulted in a high specific growth rate (µ ≈ 0.1 h−1) and high specific productivity (Psp ≈ 1 g dw L−1 d−1). The principles of increasing the efficiency of the intensive cultivation of C. sorokiniana IPPAS C-1 are discussed. These principles are relevant for the development of technological regimes for the industrial production of Chlorella in flat-panel PBRs of various sizes. [ABSTRACT FROM AUTHOR]

Systemic analysis of stress-induced transcription in the cyanobacterium Synechocystis sp. strain PCC 6803 identifies a number of genes as being induced in response to most abiotic stressors (heat, osmotic, saline, acid stress, strong light, and ultraviolet radiation). Genes for heat-shock proteins (HSPs) are activated by all these stresses and form a group that universally responds to all environmental changes. The functions of universal triggers of stress responses in cyanobacteria can be performed by reactive oxygen species (ROS), in particular H2O2, as well as changes in the redox potential of the components of the photosynthetic electron transport chain. The double mutant of Synechocystis sp. PCC 6803 (katG/tpx, or sll1987/sll0755), which is defective in antioxidant enzymes catalase (KatG) and thioredoxin peroxidase (Tpx), cannot grow in the presence of exogenous hydrogen peroxide (H2O2); and it is extremely sensitive to low concentrations of H2O2, especially under conditions of cold stress. Experiments on this mutant demonstrate that H2O2 is involved in regulation of gene expression that responds to a decrease in ambient temperature, and affects both the perception and the signal transduction of cold stress. In addition, they suggest that formation of ROS largely depends on the physical state of the membranes such as fluidity or viscosity. In cyanobacteria, an increase in membrane turnover leads to a decrease in the formation of ROS and an increase in resistance to cold stress. Therefore: (1) H2O2 is the universal trigger of stress responses in cyanobacterial cells; (2) ROS formation (in particular, H2O2) depends on the physical properties of both cytoplasmic and thylakoid membranes; (3) The destructive effect of H2O2 is reduced by increasing of fluidity of biological membranes. [ABSTRACT FROM AUTHOR]

SUMMARY: Correctly identifying species of Chlorella‐like microalgae is difficult because of their morphological simplicity and high phenotypic plasticity. The use of molecular tools has revolutionized research on algal diversity, enabling such advances as the discovery of numerous new taxa. This article presents the results of a study of strains that are newly isolated from a freshwater Lake Prudovikov (Samara region, Russian Federation). These strains had the typical Chlorella morphology, exhibiting spherical cells and a cup‐shaped parietal chloroplast. The chloroplast contained a single pyrenoid enveloped by starch grains. However, 18S–ITS1–5.8S–ITS2 sequence analyses indicated that the studied strains are strongly allied with the well‐supported genus Micractinium. Based on the results of a comparative analysis of the morphological, molecular and environmental characteristics of the studied strains (employing a polyphasic approach), we propose that they are new species of Micractinium: Micractinium kostikovii sp. nov. [ABSTRACT FROM AUTHOR]

Despite many publications about Chlorella-like algae, their reliable and accurate identification is still difficult due to their simplicity and high phenotypic plasticity. The molecular approach has revolutionized our understanding of the diversity of 'small green balls', and a natural classification of this group is currently being developed. This work is aimed at providing a detailed study of the phylogenetic position, morphology, ultrastructure, and physiology of the biotechnologically remarkable Chlorella-like strain IPPAS C-1210. Based on the SSU–ITS1–5.8S–ITS2 phylogeny, genetic distances, and the presence of compensatory base changes (CBCs) in ITS1 and conserved regions of ITS2 secondary structures, we describe a new genus, Neochlorella, with IPPAS C-1210 as the authentic strain of the type species, N. semenenkoi gen. and sp. nov. In addition, we justify the reassignment of the strain C. thermophila ITBB HTA 1–65 into N. thermophila comb. nov. The distinctive ultrastructural and physiological traits of the new species are discussed. [ABSTRACT FROM AUTHOR]

Under certain conditions, cyanobacteria can switch from photosynthesis to hydrogen production, which is a good energy carrier. However, the biological diversity of hydrogen-releasing cyanobacteria has a great unexplored potential. This study is aimed to investigate the ability of new strains of cyanobacteria Cyanobacterium sp. IPPAS B-1200, Dolichospermum sp. IPPAS B-1213, and Sodalinema gerasimenkoae IPPAS B-353 to release H 2 and to evaluate the effects of photosystem II inhibitor 3-(3,4-dichlorphenyl)-1,1-dimethylurea (DCMU) on H 2 production under light and dark conditions. The results showed that cultures treated with DCMU produced several times more H 2 than untreated cells. The highest rate of H 2 photoproduction of 4.24 μmol H 2 (mg Chl a h)−1 was found in a Dolichospermum sp. IPPAS B-1213 culture treated with 20 μM DCMU. [Display omitted] • The ability of three new cyanobacterial strains to release hydrogen was studied. • The highest H2 yield was in the Dolichospermum sp. IPPAS B-1213 strain under light anaerobic conditions. • Sodalinema gerasimenkoae IPPAS B-353 released hydrogen only in the dark. • H2 production rate increased in presence of photosynthesis inhibitor. [ABSTRACT FROM AUTHOR]

In living cells, the perception of environmental stress and the subsequent transduction of stress signals are primary events in the acclimation to changes in the environment. Some molecular sensors and transducers of environmental stress cannot be identified by traditional and conventional methods. Based on genomic information, a systematic approach has been applied to the solution of this problem in cyanobacteria, involving mutagenesis of potential sensors and signal transducers in combination with DNA microarray analyses for the genome-wide expression of genes. Forty-five genes for the histidine kinases (Hiks), 12 genes for serine-threonine protein kinases (Spks), 42 genes for response regulators (Rres), seven genes for RNA polymerase sigma factors, and nearly 70 genes for transcription factors have been successfully inactivated by targeted mutagenesis in the unicellular cyanobacterium Synechocystis sp. PCC 6803. Screening of mutant libraries by genome-wide DNA microarray analysis under various stress and non-stress conditions has allowed identification of proteins that perceive and transduce signals of environmental stress. Here we summarize recent progress in the identification of sensory and regulatory systems, including Hiks, Rres, Spks, sigma factors, transcription factors, and the role of genomic DNA supercoiling in the regulation of the responses of cyanobacterial cells to various types of stress. [ABSTRACT FROM AUTHOR]

Chloroflexales bacteria are mostly known as filamentous anoxygenic phototrophs that thrive as members of the microbial communities of hot spring cyanobacterial mats. Recently, we described many new Chloroflexales species from non-thermal environments and showed that mesophilic Chloroflexales are more diverse than previously expected. Most of these species were isolated from aquatic environments of mid-latitudes. Here, we present the comprehensive characterization of a new filamentous multicellular anoxygenic phototrophic Chloroflexales bacterium from an Arctic coastal environment (Kandalaksha Gulf, the White Sea). Phylogenomic analysis and 16S rRNA phylogeny indicated that this bacterium belongs to the Oscillochloridaceae family as a new species. We propose that this species be named ‘Candidatus Oscillochloris kuznetsovii’. The genomes of this species possessed genes encoding sulfide:quinone reductase, the nitrogenase complex and the Calvin cycle, which indicate potential for photoautotrophic metabolism. We observed only mesophilic anaerobic anoxygenic phototrophic growth of this novel bacterium. Electron microphotography showed the presence of chlorosomes, polyhydroxyalkanoate-like granules and polyphosphate-like granules in the cells. High-performance liquid chromatography also revealed the presence of bacteriochlorophylls a, c and d as well as carotenoids. In addition, we found that this bacterium is present in benthic microbial communities of various coastal environments of the Kandalaksha Gulf. [ABSTRACT FROM AUTHOR]

Five axenic cultures of microalgae were isolated from the wastewater of Almaty city and identified as Chlorella vulgaris strain № 1, Chlorella sp. strain № 3, Scenedesmus obliquus , Phormidium foveolarum and Lyngbya limnetica . Among these strains, C. vulgaris strain № 1 was characterized by the maximum growth rate and the highest productivity. Mass cultivation of this strain in wastewater resulted in accumulation of 5 × 10 7 cells per ml in 16 days, and in the removal of ∼95% of pollutants from water. Cells of C. vulgaris consisted of ∼35% proteins, 29% carbohydrates, 30% lipids, and 6% ash, as calculated on a dry weight basis. The major fatty-acids of C. vulgaris were represented by palmitic, cis -7,10-hexadecenoic acid, linoleic, and α-linolenic acids. Culturing in wastewater decreased the unsaturation index of FAs. Thus, C. vulgaris cells are suitable for both waste water purification and accumulation of biomass for further biodiesel production. [ABSTRACT FROM AUTHOR]

The organization of carbonic anhydrase (CA) system in halo- and alkaliphilic cyanobacterium Rhabdoderma lineare was studied by Western blot analysis and immunocytochemical electron microscopy. The presence of putative extracellular α-CA of 60 kDa in the glycocalyx, forming a tight sheath around the cell, and of two intracellular β-CA is reported. We show for the first time that the β-CA of 60 kDa is expressed constitutively and associated with polypeptides of photosystem II (β-CA-PS II). Another soluble β-CA of 25 kDa was induced in low-bicarbonate medium. Induction of synthesis of the latter β-CA was accompanied by an increase in the intracellular pool of inorganic carbon, which suggests an important role of this enzyme in the functioning of a CO2-concentrating mechanism. [Copyright &y& Elsevier]

We present the results of a study of mesophilic anoxygenic phototrophic Chloroflexota bacteria from Mechigmen hot spring (the Chukotka Peninsula) and Siberia. According to 16S rRNA phylogenetic analysis, these bacteria belong to Oscillochloris trichoides. However, sequencing the draft genome of the bacterium from the Chukotka and analysis of the average nucleotide identity, as well as in silico DNA-DNA hybridization, reveal that this bacterium belongs to a novel species within the Oscillochloris genus. We, therefore, propose ' Candidatus Oscillochloris fontis' as a novel taxon to represent this mesophilic alkaliphilic anaerobic anoxygenic phototrophic bacterium. Spectrophotometry and high-performance liquid chromatography analysis show that the bacterium possesses bacteriochlorophylls c and a, as well as lycopene, β-carotene and γ-carotene. In addition, transmission electron microscopy shows the presence of chlorosomes, polyhydroxyalkanoate- and polyphosphate-like granules. The genome of ' Ca. Oscillochloris fontis' and the Siberian strains of Oscillochloris sp. possess the key genes for nitrogenase complex (nif H) and ribulose-1,5-bisphosphate carboxylase/oxygenase (cbb L), as previously described for O. trichoides DG-6. The results presented here, and previously published data, show that Oscillochloris bacteria from different aquatic environments have the potential for CO2 and N2 fixation. Additionally, we describe a new primer system for the detection of RuBisCo form I. [ABSTRACT FROM AUTHOR]