[Algo-bacterial communities of the Kulunda steppe (Altai region, Russia) soda lakes].

The composition and macroscopic structure of the floating oxygenic phototrophic communities from Kulunda steppe soda lakes (Petukhovskoe sodovoe, Tanatara VI, and Gorchiny 3) was described based on the data of the 2011 and 2012 expeditions (Winogradsky Institute of Microbiology). The algo-bacterial community with a green alga Ctenocladus circinnatus as an edificator was the typical one. Filamentous Geitlerinema sp. and Nodosilinea sp. were the dominant cyanobacteria. Apart from C. circinnatus, the algological component of the community contained unicellular green algae Dunaliella viridis and cf. Chlorella minutissima, as well as diatoms (Anomeoneis sphaerophora, Brchysira brebissonii, Brachysira zellensis, Mastogloia pusilla var. subcapitata, Nitzschia amphibia, Nitzschia communis, and Nitzschia sp.1). The latter have not been previously identified in the lakes under study. In all lakes, a considerable increase in salinity was found to result in changes in the composition and macroscopic structure of algo-bacterial communities.

[Diversity of diazotrophs in the sediments of hypersaline salt and soda lakes analyzed with the use of the nifH gene as a molecular marker].

Phylogenetic analysis of the nifH genes, encoding the Fe protein of the nitrogenas enzymatic complex, was carried out for pure cultures of anoxygenic phototrophic bacteria of diverse origin, as well as for heterotrophic alkaliphilic sulfate reducers isolated from saline and soda lakes. Topology of the nitrogenase tree correlated with that of the 16S rRNAgene tree to a considerable degree; which niade it possible to use the nifH gene as a molecular marker for investigation of diazotrophic bacterialcommunities in silty sediments of saline and sodalakes. Although diazotrophs were revealed in all environmentalsamples, their phylogenetic diversity was relatively low. Sulfate-reducing deltaproteobacteria and photo- and chemotrophicgammaproteobacteria were predominant in samples integrated over sediment thickness. Analysis of samples fromthe upper sediment layers revealed predominance of phototrophic diazotrophs of various phyla, including purple sulfur and nonsulfur proteobacteria, green nonsulfur bacteria, heliobacteria; and cyanobacteria. Some phylotypes could not be identified, probably indicating the presence of bacterial groups which have not yet been studied by conventional microbiological techniques.

[Halomonas chromatireducens sp. nov., a new denitrifying facultatively haloalkaliphilic bacterium from soda salt marshes capable of aerobic chromate reduction].

A heterotrophic bacterial strain AGD 8-3 capable of denitrification under extreme haloalkaline conditions was isolated from soda solonchak soils of the Kulunda steppe (Russia). The strain was classified within the genus Halomonas. According to the results of 16S rRNA gene sequencing, Halomonas axialensis, H. meridiana, and H. aquamarina are most closely related to strain AGD 8-3 (96.6% similarity). Similar to other members of the genus, the strain can grow within a wide range of salinity and pH. The strain was found to be capable of aerobic reduction of chromate and selenite on mineral media at 160 g/l salinity and pH 9.5-10. The relatively low level of phylogenetic similarity and the phenotypic characteristics supported classification of strain AGD 8-3 as a new species Halomonas chromatireducens.

[The new bacteriochlorophyll a-containing bacterium Roseinatronobacter monicus sp. nov. from the hypersaline soda Mono Lake (California, United States)].

Two strains of pink-colored aerobic bacteriochlorophyll a-containing bacteria were isolated from aerobic (strain ROS 10) and anaerobic (strain ROS 35) zones of the water column of Mono Lake (California, United States). Cells of the bacteria were nonmotile oval gram-negative rods multiplying by binary fission by means of a constriction. No intracellular membranes were detected. Polyphosphates and poly-1-hydroxybutyric acid were the storage compounds. Pigments were represented by bacteriochlorophyll a and carotenoids of the spheroidene series. The strains were obligately aerobic, mesophilic (temperature optimum of 25-30 degrees C), alkaliphilic (pH optimum of 8.5-9.5), and halophilic (optimal NaCl concentration of 40-60 g/l). They were obligately heterotrophic and grew aerobically in the dark and in the light. Respiration was inhibited by light at wavelengths corresponding to the absorption of the cellular pigments. The substrate utilization spectra were strain-specific. In the course of organotrophic growth, the bacteria could oxidize thiosulfate to sulfate; sulfide and polysulfide could also be oxidized. The DNA G+C content was 59.4 mol % in strain ROS 10 and 59 mol % in strain ROS 35. In their phenotypic properties, the new strains were close but not identical to the alkaliphilic bacterium Roseinatronobacter thiooxidans. The distinctions in the nucleotide sequences of the 16S rRNA genes (2%) and low DNA-DNA hybridization level with Rna. thiooxidans (22-25%) allow the new strains to be assigned to a new species of the genus Roseinatronobacter, Roseinatronobacter monicus sp. nov.

[The phototrophic community found in Lake Khilganta (an alkaline saline lake located in the southeastern Transbaikal region)].

The structure of the phototrophic community found in Lake Khilganta (the Agin-Buryat Autonomous Area), a shallow saline soda lake (depth, 35-45 cm; water mineralization, 45 g/l; alkalinity, 30 mg-equiv/l; pH 9.5) has been studied. The bottom of the lake is covered with a 10- to 15-mm microbial mat, whose basis is formed by the filamentous cyanobacterium Microcoleus chthonoplastes. The mat exhibits pronounced layering and contains a significant amount of minerals. Six zones, which have characteristic colors and consistencies and are composed of intermittent layers, have been identified along the vertical profile. Live phototrophic bacteria have been found in the three upper zones. The bulk of the cyanobacteria is concentrated in the upper zone. In the lower zones, the development of purple bacteria has been observed. The diurnal dynamics of the vertical distribution of phototrophic microorganisms, which results from variations in the physicochemical environmental parameters, is described. Ectothiorhodospira sp. are dominant among the anoxyphotobacteria present. Their number, determined according to the inoculation method, is 10(6)-10(7) cells/ml. The purple bacteria of the genera Allochromatium, Thiocapsa, and Rhodovulum are also present. Experiments with isolated pure cultures have shown that the anoxygenic photosynthetic bacteria of Lake Khilganta are halotolerant and alkalitolerant or alkaliphilic. In liquid enrichment cultures, at pH 9.5, the ratio of anoxyphotobacteria species is close to that observed in the lake. When the pH is increased to 10.4, it is Ectothiorhodospira, which is the most adapted to life under increased mineralization and alkalinity, that predominantly develops. Photosynthetic activity has been observed in the three upper mat zones and constitutes, on average, 1.5 g C/(m2 h); the share of anoxygenic photosynthesis accounts for 75-95% of the total productivity. The main role in sulfide oxidation belongs to the phototrophic anoxyphotobacteria and cyanobacteria. In terms of the physicochemical conditions and structure of the phototrophic community, Lake Khilganta is similar to shallow saline water bodies of marine origin. The main differences consist in the increased alkalinity and in the consequent prevalence of alkaliphilic and alkalitolerant microorganisms and in the absence of representatives of the neutrophilic group of green sulfur bacteria.

[Phylogeny of ribulose-1,5-bisphosphate carboxylase/oxygenase genes in haloalkaliphilic obligately autotrophic sulfur-oxidizing bacteria of the genus Thioalkalivibrio].

Fragments of genes of the greenlike form I ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) of eight species of haloalkaliphilic obligately autotrophic sulfur-oxidizing bacteria of the genus Thioalkalivibrio have been revealed and sequenced using previously developed oligonucleotide primers. The data obtained are used for the construction of phylogenetic trees on the basis of nucleotide sequences of RuBisCO genes and their conceptual translations into amino acid sequences. Comparative analysis of the 16S rRNA and RuBisCO gene trees reveals discrepancies between their topologies. According to a RuBisCO gene analysis, the genus Thioalkalivibrio is not monophyletic, and its inner divergence conforms to the significant morphological differences observed between the species. Presumably, horizontal (interspecies) gene transfer was involved in the evolution of the genus Thioalkalivibrio.

[Alkalitolerant yeasts from natural biotopes]. / Alkalotolerantnye drozhzhi iz prirodnykh biotopov.

Using a solid nutrient medium containing alkaline buffer (pH 10) and an antibiotic, alkalitolerant yeasts were isolated from samples of soda-rich saline soils (solonchaks) of Armenia (Arazdayan) and the Transbaikal Region (the Kungur Steppe). The species diversity of the yeast populations of the tested soda-rich soils was relatively insignificant. They only contained alkalitolerant representatives of asporogenic capsulated yeasts belonging to the species Cryptococcus laurentii, C. albidus, Rhodotorula glutinis, R. mucilaginosa, and Sporobolomyces roseus. C. laurentii representatives clearly dominated the isolates obtained, their number exceeding that of the other species by 2-3 orders of magnitude. All of the isolates grew on acidic wort agar, suggesting that they did not include obligate alkaliphiles.

[Resting forms of gram negative chemolithoautotrophic bacteria Thioalkalivibrio versutus and Thioalkalimicrobium aerophilum]. / Obrazovanie pokoiashchikhsia form u gramotritsatel'nykh khemolitoavtotrofnykh bakterii Thioalkalivibrio versutus i 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.

[Oxidation of inorganic sulfur compounds by obligatory organotrophic bacteria]. / Okislenie neorganicheskikh sernykh soedinenii obligatno khemogeterotrofnymi bakteriiami.

New data obtained by the author and other researchers on two different groups of obligately heterotrophic bacteria capable of inorganic sulfur oxidation are reviewed. Among culturable marine and (halo)alkaliphilic heterotrophs oxidizing sulfur compounds (thiosulfate and, much less actively, elemental sulfur and sulfide) incompletely to tetrathionate, representatives of the gammaproteobacteria, especially from the Halomonas group, dominate. Some of denitrifying species from this group are able to carry out anaerobic oxidation of thiosulfate and sulfide using nitrogen oxides as electron acceptors. Despite the low energy output of the reaction of thiosulfate oxidation to tetrathionate, it can be utilized for ATP synthesis by some tetrathionate-producing heterotrophs; however, this potential is not always realized during their growth. Another group of marine and (halo)alkaliphilic heterotrophic bacteria capable of complete oxidation of sulfur compounds to sulfate mostly includes representatives of the alphaproteobacteria most closely related to nonsulfur purple bacteria. They can oxidize sulfide (polysulfide), thiosulfate, and elemental sulfur via sulfite to sulfate but neither produce nor oxidize tetrathionate. All of the investigated sulfate-forming heterotrophic bacteria belong to lithoheterotrophs, being able to gain additional energy from the oxidation of sulfur compounds during heterotrophic growth on organic substrates. Some doubtful cases of heterotrophic sulfur oxidation described in the literature are also discussed.

[Roseinatronobacter thiooxidans Gen. Nov., sp. Nov., a new alkaliphilic aerobic bacteriochlorophyll-alpha-containing bacteria from a soda lake]. / Roseinatronobacter thiooxidans Gen. Nov., sp. Nov., novaia alkalofil'naia bakteriokhlorofill-a-soderzhashchaia bakteriia iz sodovogo ozera.

Several samples of microbial mat obtained from soda lakes of the Kunkurskaya steppe (Chita oblast) abundantly populated by purple bacteria were screened for the presence of heterotrophic alkaliphiles capable of oxidizing sulfur compounds to sulfate. This capacity was found in only one pigmented strain, ALG 1, isolated on medium with acetate and thiosulfate at pH 10. The strain was found to be a strictly aerobic and obligately heterotrophic alkaliphile. Growth on medium with acetate was possible within a narrow pH range from 8.5 to 10.4. The strain formed a reddish orange carotenoid and bacteriochlorophyll a. Pigments were synthesized only at high concentrations of nitrogen-containing organic compounds (peptone or yeast extract). The production of bacteriochlorophyll a was maximal under microaerobic conditions in darkness. Strain ALG 1 could oxidize sulfide, thiosulfate, sulfite, and elemental sulfur to sulfate. In heterotrophically growing culture (pH 10), thiosulfate was not oxidized until the late logarithmic phase. The sulfur-oxidizing activity was maximal at the most alkaline pH values. The notable increase in the efficiency of organic carbon utilization observed in the presence of thiosulfate suggested that the bacterium was a sulfur-oxidizing lithoheterotroph. The phylogenetic analysis of the 16S rRNA gene showed strain ALG 1 to be a member of the alpha-3 subgroup of proteobacteria and to constitute a distinct branch located between nonsulfur purple bacteria Rhodobacter and Rhodovulum. Based on the unique phenotypic properties and the results of phylogenetic analysis, the alkaliphilic isolate ALG 1 was assigned to a new genus and species Roseinatronobacter thiooxidans with the type strain DSZM-13087.

[Biological oxidation of a sulfur atom in single-carbon and organic compounds]. / Biologicheskoe okislenie atoma sery v sostave odnouglerodnykh i organicheskikh soedinenii.

Oxidation of sulphur of various natural and artificial sulphur-containing organic compounds by macro- and microorganisms is reviewed. It includes data on microbial oxidation of volatile organic sulphides, oxidation of CNS-, cystine and thiophenes as natural S-compounds and biological S-oxidation of xenobiotics.