[Resting forms of gram negative chemolithoautotrophic bacteria Thioalkalivibrio versutus and Thioalkalimicrobium aerophilum]

The haloalkaliphilic chemoautotrophic gram-negative bacteria Thioalkalivibrio versutus, strain AL2, and Thioalkalimicrobium aerophilum, strain AL3, were shown to possess the capacity to produce resting forms, namely cyst-like refractile cells (CRC), whose production was controlled by the level of the d1 extracellular factors, exhibiting the function of anabiosis autoinducers. The conditions were elucidated that promoted the formation of CRC in the developmental cycles of the cultures studied, in condensed cell suspensions undergoing autolysis, and under the action of exogenously introduced chemical analogues of anabiosis autoinducers (alkylhydroxybenzenes). The peculiarities of the fine structure of the resting cells obtained were studied. Distinctions were revealed (with respect to viability and thermotolerance) between the CRC formed under different conditions. The relationship between the growth strategy and survival strategy of extremophilic bacteria is discussed with taking into account the effect of the d1 autoregulatory factors. A new model of CRC formation is proposed: CRC production in the life cycle of bacteria developing under conditions of increased concentration of anabiosis autoinducers.

[Mats of Microcoleus from alkaliphilic and halophilic communities]

A detailed description of the macrostructure, the ultrastructure, and the species diversity of alkaliphilic mat from Lake Khilganta (Buryatiya) is presented. The structure of this mat was found to be similar to that of halophilic mats from hypersaline lagoons of Lake Sivash (Crimea) that we studied earlier. Microcoleus chthonoplastes was the dominant form of cyanobacteria in both mats (in the alkaliphilic mat, Phormidium molle was another dominant form). Both mats had a pronounced laminated structure. However, unlike halophilic mats with calcium carbonate and gypsum laminas, the alkaliphilic mat contained calcium phosphate laminas instead of gypsum ones. The species diversity of microorganisms in the alkaliphilic mat was at least as rich as that in the halophilic mat; however, in the halophilic mat, the distribution of organisms between layers was more clear-cut. In the alkaliphilic mat, the highest species diversity was observed in the upper mat layers at the boundary between zones of oxygenic and anoxygenic photosynthesis. This fact can be explained by the ephemeral nature of soda lakes.

[Utilization of methane and carbon dioxide by symbiotrophic bacteria in gills of Mytilidae (Bathymodiolus) from the Rainbow and Logachev hydrothermal fields on the Mid-Atlantic Ridge]

Bivalve mollusks Bathymodiolus asoricus and Bathymodiolus puteoserpentis collected from the Rainbow and Logachev hydrothermal fields during dives of Mir 1 and Mir 2 deep-sea manned submersibles were studied. Rates of methane oxidation and carbon dioxide assimilation in mussel gill tissue were determined by radiolabel analysis. During oxidation of 14Ch4, radiocarbon was detected in significant quantities not only in carbon dioxide but also in dissolved organic matter, most notably 14C-formate and 14C-acetate, occurring in a 2:1 ratio. Activities of hexulose-phosphate synthase, phosphoribulokinase, and ribulose 1,5-bisphosphate carboxylase were shown in the soluble fraction of gill tissue cells. At the same time, no activity of hydroxypyruvate reductase--the key enzyme of the serine pathway of C1-assimilation--was detected. The results of PCR amplification using genetic probes for membrane-bound methane monooxygenase (pmoA) and methanol dehydrogenase (mxaF) attest to the presence of the genes of these enzymes in the total DNA extracted from gill samples. However, no appropriate PCR responses were obtained with the mmoX primer system, which is a marker for soluble methane monooxygenase. All samples studied showed amplification with primers for the genera Methylobacter and Methylosphaera. At the same time, no genes specific to the genera Methylomonas, Methylococcus, Methylomicrobium, or Methylosinus and Methylocystis were detected. Electron microscopic examinations revealed the presence of two groups of endosymbiotic bacteria in the mussel gill tissue. The first group was represented by large cells possessing a complex system of cytoplasmic membranes, typical of methanotrophs of morphotype I. The other type of endosymbionts, having much smaller cells and lacking intracellular membrane structures, is likely to be constituted by sulfur bacteria.

[Desulfacinum subterraneum sp.nov.--a new thermophilic sulfate-reducing bacterium isolated from a high temperature oil field ]

A new thermophilic sulfate-reducing bacterium isolated from the high-temperature White Tiger oil field (Vietnam) is described. Cells of the bacterium are oval (0.4-0.6 by 0.6-1.8 microns), nonmotile, non-spore-forming, and gram-negative. Growth occurs at 45 to 65 degrees C (with an optimum at 60 degrees C) at NaCl concentrations of 0 to 50 g/l. In the course of sulfate reduction, the organism can utilize lactate, pyruvate, malate, fumarate, ethanol, salts of fatty acids (formate, acetate, propionate, butyrate, caproate, palmitate), yeast extract, alanine, serine, cysteine, and H2 + CO2 (autotrophically). In addition to sulfate, the bacterium can use sulfite, thiosulfate, and elemental sulfur as electron acceptors. In the absence of electron acceptors, the bacterium can ferment pyruvate and yeast extract (a yet unrecognized capacity of sulfate reducers) with the formation of acetate and H2. The G + C content of DNA is 60.8 mol %. The level of DNA-DNA hybridization of the isolate (strain 101T) and Desulfacinum infernum (strain B alpha G1T) is as low as 34%. Analysis of the nucleotide sequence of 16S rDNA places strain 101T in the phylogenetic cluster of the Desulfacinum species within the sulfate reducer subdivision of the delta subclass of Proteobacteria. All these results allowed the bacterium studied to be described as a new species, Desulfacinum subterraneum sp. nov., with strain 101 as the type strain.

[Heliobacterium sulfidophilum sp. Nov. and Heliobacterium undosum sp. Nov.: sulfide-oxidizing Heliobacteria from thermal sulfidic springs]

Two new species of heliobacteria isolated from cyanobacterial mats of two alkaline sulfidic hot springs are formally described. Strains BR4 and BG29 are assigned to anoxygenic phototrophic bacteria of the family Heliobacteriaceae, since they possess the unique properties of this taxon: strict anaerobiosis, formation of bacteriochlorophyll g, the lack of extensive intracytoplasmic membranes and chlorosomes, an unusual cell wall structure, and phylogenetic relatedness to the low G + C gram-positive eubacteria. Based on the 16S rDNA sequence similarity, strains BR4 and BG29 are assigned to the genus Heliobacterium and described as two new species of this genus: Heliobacterium sulfidophilum sp. nov. and Heliobacterium undosum sp. nov. The G + C content of the DNA is 51.3 mol % in Hbt. sulfidophilum and 57.2-57.7 mol % in Hbt. undosum. The cells of Hbt. sulfidophilum are rods, and the cells of Hbt. undosum are slightly twisted spirilla or short rods. Both new bacteria are motile by peritrichous flagella. Hbt. sulfidophilum produces endospores. The new bacteria are strict anaerobes growing photoheterotrophically on a limited range of organic compounds. In the dark, they can switch from photosynthesis to the slow fermentation of pyruvate. Biotin is required as a growth factor. Both species are highly tolerant to sulfide (up to 2 mM at pH 7.5) and oxidize it photoheterotrophically to elemental sulfur; photoautotrophic growth was not observed. The temperature optimal for growth of Hbt. sulfidophilum and Hbt. undosum is 30-35 degrees C, and the optimal pH is 7-8.

[Characteristics of morphology and ultrastructure of bacteria of the genus Dethiosulfovibrio]

Cell morphology and fine structure were studied in two strains of rod-shaped, strictly anaerobic, gram-negative sulfidogenic bacteria: strain SR12T (DSM 12538) and strain WS100 (DSM 12537) belonging to "Dethiosulfovibrio starorussensis." Cells of both strains, as well as cells of the type species of the genus Dethiosulfovibrio, D. peptidovorans, were found to possess multiple intracellular incomplete cross septa in the stationary growth phase.

[Formation of resting refractile cells in Bacillus cereus as affected by an autoregulatory factor]

Extracellular membrane-active compounds were shown to induce the transition of vegetative cells in the producing culture into resting refractile forms. The forms are characterized by the absence of energy, biosynthetic and destructive processes, by the capability to remain viable for a long time, and by a peculiar ultrafine organization. The physiological state and the ultrafine organization of B. cereus cells were found to change under the action of the autoregulatory factor introduced in the culture.

[Ultrastructural characteristics of Actinomyces olivaceus in the process of development of a culture as related to lipid synthesis]

The cytomorphology of an Actinomyces olivaceus culture was studied, in the course of its submerged cultivation in two media differing in phosphate content, in relation to lipid biosynthesis. The cells (including those grown under the conditions of phosphate deficiency in the medium) have well-developed membranous apparatus, particularly during the exponential growth phase and in the transition to the stationary phase whose time depends on the composition of the medium. No visible defects were found in the membranous apparatus of cells grown under the conditions of phosphate deficiency; the lipid component of these cells contained ornithinolipid instead of phosphatidyl ethanolamine. The fraction of ornithinolipid which had been found in this culture only under the conditions of phosphate deficiency was detected now in cells cultivated in a medium lacking CoCl2.6H2O but without phosphate deficiency during the stationary growth phase using the techniques of column and thin-layer chromatography. Nitrogen-containing polar lipids comprise cephalin (86.5%) and ornithinolipid (13.3%).

[Regulation of Pseudomonas carboxydoflava growth and development by specific endogenous factors]

It was established for the first time that Pseudomonas carboxydoflava synthesizes a specific autoregulator factor (d) in the process of growth; the factor is a membrane-active compound according to the mode of its action. The regulatory action of the factor is manifested in limiting the number of the cellular population of the producing culture and in the capacity to induce the transition of vegetative cells into the resting state. The new forms are characterized by the abruptly decreased level fo metabolism, the high degree of light refraction, a peculiar ultrastructural organization, and the ability to retain viability for a long period of time.

[Electron microscopic study of normal Bacillus anthracoides spores and after exposure to a chloroactive disinfectant]

The fine structure of Bacillus anthracoides spores is similar in general to that of other, taxonomically related species of spore forming bacteria. However, the former is characterized by a well-developed multilayered exosporium and the heterogeneous structure of an envelope. The lethal effect of a chloroactive disinfectant (2/3 of calcium hypochlorite basic salt) is caused by changes in the structural organization of spores, which interferes with the normal permeability barrier and metabolic processes.