Abstract:
Picocyanobacteria, the smallest cell-size cyanobacteria, are numerous and ubiquitous in freshwater, brackish, and marine environments. In freshwater, they are represented mainly by genera including Synechococcus, Cyanobium, and Synechocystis, and in marine waters, predominantly by Synechococcus and Prochlorococcus. Several Synechocystis and Synechococcus isolates from freshwater and brackish environments were found to produce hepatotoxins from the microcystin group. A strain of Synechococcus from the Salton Sea, capable of microcystin-LR and microcystin-YR production, was shown to be closely related to marine Synechococcus. A Synechococcus strain isolated from the Mazurian Lake Bełdany was shown to have mcy genes, closely related to the Planktothrix mcy-gene cluster. Other results suggest that picocyanobacteria may be also a source of neurotoxins (neurotoxin β-N-methylamino-l-alanine), lipopolysaccharides, taste, and odour compounds as well as cytotoxic and antimicrobial compounds. These findings suggest that picocyanobacteria can be a new potential source of toxins and other bioactive compounds in freshwaters and marine environments that have, so far, been overlooked.Keywords:
Synechocystis
Cyanobacteria are an important group of microorganisms displaying a range of morphologies that enable phenotypic differentiation between the major lineages of cyanobacteria, often to the genus level, but rarely to species or strain level. We focused on the unicellular genus Synechocystis that includes the model cyanobacterial strain PCC 6803. For 11 Synechocystis members obtained from cell culture collections, we sequenced the variable part of the 16S rRNA-encoding region and the 16S - 23S internally transcribed spacer (ITS), both standardly used in taxonomy. In combination with microscopic examination we observed that 2 out of 11 strains from cell culture collections were clearly different from typical Synechocystis members. For the rest of the samples, we demonstrated that both sequenced genomic regions are useful for discrimination between investigated species and that the ITS region alone allows for a reliable differentiation between Synechocystis strains.
Synechocystis
Strain (injury)
23S ribosomal RNA
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Picocyanobacteria, the smallest cell-size cyanobacteria, are numerous and ubiquitous in freshwater, brackish, and marine environments. In freshwater, they are represented mainly by genera including Synechococcus, Cyanobium, and Synechocystis, and in marine waters, predominantly by Synechococcus and Prochlorococcus. Several Synechocystis and Synechococcus isolates from freshwater and brackish environments were found to produce hepatotoxins from the microcystin group. A strain of Synechococcus from the Salton Sea, capable of microcystin-LR and microcystin-YR production, was shown to be closely related to marine Synechococcus. A Synechococcus strain isolated from the Mazurian Lake Bełdany was shown to have mcy genes, closely related to the Planktothrix mcy-gene cluster. Other results suggest that picocyanobacteria may be also a source of neurotoxins (neurotoxin β-N-methylamino-l-alanine), lipopolysaccharides, taste, and odour compounds as well as cytotoxic and antimicrobial compounds. These findings suggest that picocyanobacteria can be a new potential source of toxins and other bioactive compounds in freshwaters and marine environments that have, so far, been overlooked.
Synechocystis
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в настоящее время все более широкое распространение в ток-сикологических и санитарно-гигиенических исследованиях получают так называемые «альтернативные методы» изучения токсичности с использованием микроорганизмов различных видов.цианобактерии являются обычными обитателями водоемов раз-личного назначения [2, 4]. Представляется, что применение этих одноклеточных микроорганизмов в качестве тест-объектов, с одной стороны, для оценки загрязнения водоемов, с другой – для изучения токсичности вредных химических веществ является перспективным для экологических и токсикологических исследований. цель исследования состояла в экспериментальной оценке чувстви-тельности цианобактерий разных штаммов к токсическому действию солей тяжелых металлов в разных условиях температуры и освещен-ности окружающей среды. Материалы и методы исследованияв работе использовались штаммы цианобактерий Synechocystis sp. PCC 6803 из коллекции цианобактерий Санкт-Петербургского государ-ственного университета и Synechocystis sp. CALU 713 из коллекции московского государственного университета.культивирование проводилось в жидкой минеральной среде № 6 [1] в колбах вместимостью 200–250 мл при температуре 23 oС и непре-рывном освещении люминесцентными лампами 2 300 лк. для эксперимента использовался штамм в активной фазе роста. Посевной материал инокулировался в пробирки с 4,5 мл жидкой минеральной среды № 6, разведенной в 10 раз с добавлением 4,5 мл солей металлов (AgNO
Synechocystis
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The marine sponge Xestospongia muta (Porifera: Demospongiae: Haplosclerida) harbours cyanobacteria in its peripheral tissue that have been described as having an Aphanocapsa feldmanni-type appearance. Through subsequent cell fractionation steps we obtained a virtually pure cell suspension of the cyanobacteria. Through amplification of a region of the 16S rRNA gene we found that these cyanobacteria seem closely related to Prochlorococcus (Cyanobacteria, Prochlorophytes, Prochlorococcaceae), and Synechococcus (Cyanobacteria, Chroococcales, Synechococcus). We furthermore developed a new method, to obtain a clear signal with FISH by bleaching the auto-fluorescence of cyanobacteria, with osmium tetroxide. The location and morphological characteristics of the cyanobacteria are described by both light and electron microscopy.
Sponge
Prochlorococcus
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Glutamine synthetases (GSs) from two cyanobacteria, one unicellular (Synechocystis sp. strain PCC 6803) and the other filamentous (Calothrix sp. strain PCC 7601 [Fremyella diplosiphon]), were purified to homogeneity. The biosynthetic activities of both enzymes were strongly inhibited by ADP, indicating that the energy charge of the cell might regulate the GS activity. Both cyanobacteria exhibited an ammonium-mediated repression of GS synthesis. In addition, the Synechocystis sp. showed an inactivation of GS promoted by ammonium that had not been demonstrated previously in cyanobacteria.
Synechocystis
Strain (injury)
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Synechocystis
Peroxiredoxin
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Synechocystis
Cryo-Electron Microscopy
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Synechocystis
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The marine picocyanobacterium Synechococcus sp. strain WH7803 possesses two glutamine synthetases (EC 6.3.2.1), GSI encoded by glnA and GSIII encoded by glnN. This is the first work addressing the physiological regulation of both enzymes in a marine cyanobacterial strain. The increase of GS activity upon nitrogen starvation was similar to that found in other model cyanobacteria. However, an unusual response was found when cells were grown under darkness: the GS activity was unaffected, reflecting adaptation to the environment where they thrive. On the other hand, we found that GSIII did not respond to nitrogen availability, in sharp contrast with the results observed for this enzyme in other cyanobacteria thus far studied. These features suggest that glutamine synthetase activities in Synechococcus sp. WH7803 represent an intermediate step in the evolution of cyanobacteria, in a process of regulatory streamlining where GSI lost the regulation by light, while GSIII lost its responsiveness to nitrogen. This is in good agreement with the phylogeny of Synechococcus sp. WH7803 in the context of the marine cyanobacterial radiation.
Darkness
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Indications of differential transcriptional regulation of fatty acid synthesis in the model cyanobacteria Synechocystis sp. Strain PCC 6803 and Synechococcus elongatus PCC 7942
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Strain (injury)
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