Molecular identification and ultrastructural and phylogenetic studies of cyanobacteria from association with the white sea hydroid Dynamena pumila (L., 1758).

Three new cyanobacterial strains, that have been previously purified from the hydroid Dynamena pumila (L., 1758), isolated from the White Sea, were studied using scanning and transmission electron microscopy methods and were characterized by using almost complete sequence of the 16S rRNA gene, internal transcribed spacer 16S-23S rRNA, and part of the gene for 23S rRNA. The full nucleotide sequences of the rRNA gene clusters were deposited to GenBank (HM064496.1, GU265558.1, JQ259187.1). Comparison of rRNA gene cluster sequences of Synechococcus cyanobacterium 1Dp66E-1, Oscillatoriales cyanobacterium 2Dp86E, and Nostoc sp. 10Dp66E with all sequences present at the GenBank shows that these cyanobacterial strains do not have 100% identity with any organisms investigated previously. Furthermore, for the first time heterotrophic bacterium, associated with Nostoc sp. 10Dp66E, was identified as a member of the new phylum Gemmatimonadetes, genus of Gemmatimonas (GenBank accession number is JX437625.1). Phylogenetic analysis showed that cyanobacterium Synechococcus sp. 1Dp66E-1 forms the unique branch and belongs to a cluster of Synechococcus, including freshwater and sea strains. Oscillatoriales cyanobacterium 2Dp86E belongs to a cluster of Leptolyngbya strains. Isolate Nostoc sp. 10Dp66E forms unique branch and belongs to a cluster of the genus Nostoc, with the closest relative of Nostoc commune isolates.

The pleiotropic effects of ftn2 and ftn6 mutations in cyanobacterium Synechococcus sp. PCC 7942: an ultrastructural study.

Two cell division mutants (Ftn2 and Ftn6) of the cyanobacterium Synechococcus sp. PCC 7942 were studied using scanning electron microscopy and transmission electron microscopy methods. This included negative staining and ultrathin section analysis. Different morphological and ultrastructural features of mutant cells were identified. Ftn2 and Ftn6 mutants exhibited particularly elongated cells characterized by significantly changed shape in comparison with the wild type. There was irregular bending, curving, spiralization, and bulges as well as cell branching. Elongated mutant cells were able to initiate cytokinesis simultaneously in several division sites which were localized irregularly along the cell. Damaged rigidity of the cell wall was typical of many cells for both mutants. Thylakoids of mutants showed modified arrangement and ultrastructural organization. Carboxysome-like structures without a shell and/or without accurate polyhedral packing protein particles were often detected in the mutants. However, in the case of Ftn2 and Ftn6, the average number of carboxysomes per section was less than in the wild type by a factor of 4 and 2, respectively. These multiple morphological and ultrastructural changes in mutant cells evinced pleiotropic responses which were induced by mutations in cell division genes ftn2 and ftn6. Ultrastructural abnormalities of Ftn2 and Ftn6 mutants were consistent with differences in their proteomes. These results could support the significance of FTN2 and FTN6 proteins for both cyanobacterial cell division and cellular physiology.

[Permeability of cyanobacterial mucous surface structures for macromolecules].

The space of diffusive distribution of neutral hydrophilic macromolecules (dextrans with molecular sizes of 1.5 to 9 nm in the Stokes radius values) in the mucous surface structures (MSS) of intact bacterial cells has been studied for the first time on cyanobacteria. Cyanobacterial species and strains under study belong to different taxonomic groups, the members of which form MSS of various morphology and ultrastructure and can grow in association with plants and animals, inter alia as mucous microcolonies. The range of permeability has been determined by the fractionation of polydisperse dextrans method, previously applied for plants, in combination with electron microscopy. Dextrans are supposedly distributed in the MSS polysaccharide matrix in accordance with their sizes, in much the same way as in a macroporous unitary gel. The similarity of the chemical composition and macromolecular organization of cyanobacterial MSS with pectins of plant cell walls and the role of MSS and the intercellular matrix as permeability barriers in associative interactions of microorganisms are under consideration.

[Atypical cell forms overproducing extracellular substances in population of cycad cyanobionts]. / Neobychnye kletochnye formy s giperproduktsiei ékstratselluliarnykh veshchestv v populiatsiiakh tsianobiontov sagovnikov.

The ultrastructure of the cyanobionts of the greenhouse-grown cycads Cycas circinalis, Ceratozamia mexicana, and Encephalartos villosus was studied. The cyanobiont microcolonies grown in the intercellular space of the cyanobacterial zone of cortical parenchyma in the cycad coralloid roots contained two specific forms of vegetative cells with a reduced cell wall, namely, protoplasts and spheroplasts. The protoplasts and spheroplasts exhibited ultrastructural changes indicating the overproduction of two extracellular substances, one of which resembled the mucilage polysaccharides and the other was proteinous. The substances were likely to be synthesized intracellularly and then be excreted with the aid of surface vesicles or by channels in the cytoplasmic membrane to form, respectively, a slimy extracellular matrix and an additional electron-opaque envelope around the cell. At the late developmental stages, the excretion of these substances was accompanied by degradative changes in the cells, leading eventually to cell death. The physiological role of these specific cell forms and the factors that induce their development and death in the cell populations of cyanobionts are discussed.

[Heterocysts with reduced cell walls in populations of cycad cyanobionts]. / Geterotsisty s redutsirovannoi kletochnoi stenkoi v populiatsiiakh tsianobiontov sagovnikov.

The ultrastructure of the cyanobionts of the greenhouse-grown cycads Cycads circinalis, Ceratozamia mexicana, and Encephalartos villosus was studied. In addition to heterocysts with the typical ultrastructure, the cyanobiont microcolonies also contained altered heterocysts with reduced cell walls, which might dominate in all regions of the coralloid roots. The altered heterocysts represented a protoplast enclosed in a heterocyst-specific envelope with additional layers. Some heterocysts contained an additional reticular protoplast-enclosing sheath below the heterocyst-specific envelope, whereas the other heterocysts contained an additional electron-opaque outer layer. The substance of the inner sheath of the former heterocysts resembled the polysaccharides of mucilage, which fills the intercellular space of plant tissues, whereas the electron-opaque outer layer of the latter heterocysts probably had a protein nature. The substances that constitute the sheath and the outer layer are likely to be synthesized intracellularly and then released with the aid of membrane-bounded vesicles or by channels in the cytoplasmic membrane.

Oscillochloris trichoides neotype strain DG-6.

The new strain of filamentous green bacterium strain DG-6 was isolated in pure culture from the spring of Caucuses. The study of this bacterium allows to suggest that it is a member of the familyChloroflexaceae and may be considered asOscillochloris trichoides neotype strain. The description of this green bacterium is given.

Introduction of a nitrogen-fixing cyanobacterium into tobacco shoot regenerates.

Tobacco (Nicotiana tabacum L.) shoots associated with the nitrogen-fixing cyanobacterium Anabaena variabilis Kütz. (ATCC 29413) were regenerated in mixed cultures of tobacco callus and the cyanobacterium. The cyanobacteria were localized inside the tissues as well as on the surface of regenerated shoots, formed heterocysts, and were capable of acetylene reduction.

[Characteristics of the cellular ultrastructural organization of the chemoheterotrophic blue-green alga, Chlorogloea fritschii]. / Osobennosti ul'trastrukturnoi organizatsii kletok khemogetero-trofnoi sinezelenoi vodorosli Chlorogloea fritschii.

Cellular ultrastructural organization was compared in photoautotrophic and chemoheterotrophic cultures of the blue-green alga Chlorogloea fritschii Mitra. Cells at the fourth stage of the life cycle of the culture in the phase of growth were studied in both cases. The structure of thylakoids was the main object of investigation. The cells of investigation. The cells of Chl. fritschii had a peculiar organization when they were cultivated in the dark on a medium containing glucose as a source of carbon and energy. These cells differed from photosynthetic cells by the structure of the cell wall, cytoplasm, and thylakoids. The cell wall can be entirely or partly absent. The cytoplasm has a lower electron density. The cell wall can be entirely or partly absent. The cytoplasm has a lower electron density. The thylakoids are arranged more random and less compact than in the cells grown in the light. Membranes which form these thylakoids, under identical conditions of fixation, contrasting and microscopy of preparations, look usually as one-layered rather than three-layered. Apparently, the ultrastructure of thylakoids on Chl. fritschii reflects the specificity of energy mechanisms that function in cells in the light and in the dark.

[Electron microscopic study of dark and photo-oxidative degradation of the blue-green alga Anabaena variabilis]. / Elektronno-mikroskopicheskoe izuchenie temnovoi i fotookislitel'noi degradatsii sine-zelenoi vodorosli Anabaena variabilis

Changes in the cell ultrastructure were studied during incubation of the obligate phototrophic blue-green alga Anabaena variabilis in the dark for a long time. The cells lost viability though their cell wall and cytoplasmic membrane were preserved; however, certain regions of the mureine layer were thickened in some cells. The membranes of the photosynthetic apparatus separate forming intrathylakoid spaces and the cytoplasm density decreases revealing phycobilisomes. During incubation in the dark for a long time, polyglucoside alpha-granules in the cytoplasm disappear, polyhedral bodies are preserved, and numerous large granules of average electron density and unknown nature appear. Transfer of the culture from the dark to the light when the cells are losing their viability results in intensive destruction of the thylakoids. Loss of viability by the cells of Anabaena variabilis in the dark is supposed to be due to irreversible damages of the membranes of the photosynthetic apparatus in these conditions.

[Electron microscopic and biochemical study of spheroplasts of the blue-green alga Anabaena variabilis]. / Elektronno-mikroskopicheskoe i biodhimicheskoe izuchenie sferoplastov sine-zelenoi vodorosli Anabaena variabilis

Electron microscopy of the spheroplasts of the blue-green alga Anabaena variabilis revealed damages induced by lysozyme. Biochemical analysis confirmed the data of electron microscopy that the spheroplasts had lost partly the cytoplasmic content of the cells. DNA was preserved in the spheroplasts though the nucleoid was not detected by electron microscopy.