Description and Genomic Analysis of the First Facultatively Lithoautotrophic, Thermophilic Bacteria of the Genus Thermaerobacter Isolated from Low-temperature Sediments of Lake Baikal.

Members of the genus Thermaerobacter belong to the phylum Firmicutes and all isolates characterised to date are strictly aerobic and thermophilic. They were isolated from a mud sample of the Challenger Deep in the Mariana Trench, hydrothermal vents, and silt compost. A novel thermophilic, facultatively lithoautotrophic bacteria of the genus Thermaerobacter, strain PB12/4term (=VKM B-3151T), with a metabolism that is uncharacteristic of the type species, was isolated from low-temperature surface sediments near the Posolsk Bank methane seep, Lake Baikal, Russia. The new strain grows with molecular hydrogen as electron donor, elemental sulfur, and thiosulfate as electron acceptors, and CO2/[Formula: see text] as carbon source. The genome of strain PB12/4term consists of one chromosome with a total length of 2.820.915 bp and the G+C content of the genomic DNA was 72.2%. The phylogenomic reconstruction based on 120 conserved bacterial single-copy proteins revealed that strain PB12/4term belongs to the genus Thermaerobacter within in the class Thermaerobacteria, phylum Firmicutes_E. The strain PB12/4term is closely related to Thermaerobacter subterraneus DSM 13965 (ANI=95.08%, AF=0.91) and Thermaerobacter marianensis DSM 12885 (ANI=84.98%, AF=0.77). Genomic and experimental data confirm the ability of the Thermaerobacter PB12/4term pure culture to facultatively lithotrophic growth, which is provided by the presence of [NiFe]hydrogenase enzymes that are absent in T. marianensis DSM 12885 and T. subterraneus DSM 13965. The data obtained on the physiological and biochemical differences of strain PB12/4term provide a deeper insight into the species diversity and functional activity of the genus Thermaerobacter.

[Studies of prevalence rate of furunculosis caused by infection by Aeromonas salmonicida in salmonids of the southern part of Sakhalin Island].

Ichthyological studies of spawners of salmonids in the south of Sakhalin Island were studied. Cases of furunculosis disease were revealed. The agent of the disease Aeromonas salmonicida was isolated. Its morphological, physiological-biochemical, and antagonistic properties were studied, and the virulence of the isolated strains was determined. For supporting the species status of the studied strains of A. salmonicida, a molecular-genetic analysis was performed.

[Microbial communities and their ability to oxidize n-alkanes in the area of release of gas- and oil-containing fluids in Mid-Baikal (Cape Gorevoi Utes)].

The microbial community in the area of oil seep in Mid-Baikal (Cape Gorevoi Utes) was studied. The number of microorganisms that oxidize normal hydrocarbons, petroleum, and easily accessible organic matter in the water mass of the lake, bottom sediments, and bitumen structures was studied in 2005-2009. The high heterogeneity of the distribution of microorganisms associated with the deparaffination of oil in the areas of oil seeps was noted. The maximum concentrations of hydrocarbon-oxidizing microorganisms in the samples of bottom water above bitumen structures (up to 2200 +/- 175 CFU/ml) and in bitumen structures themselves (up to 170000 +/- 13000 CFU/g) were determined. A model experiment showed that in the conditions of low temperatures (4 degrees C) the degradation of the fraction of oil n-alkanes by the natural microbial community reaches 90% over a period of 60 days.

[Diversity of cultured aerobic microorganisms in the areas of natural oil seepage on Lake Baikal].

The diversity of cultured aerobic organisms collected from water samples and bottom sediment from two areas of natural oil seepage on Lake Baikal has been researched. Representatives of Alpha-, Beta-, and Gammaproteobacteria have been found in samples collected near the BolTshaya Zelenovskaya River mouth, while near Cape Gorevoi Utes Betaproteobacteria were absent. Most cultures are characterized by a sufficiently high homology level (96-100%) with nucleotide sequences from the international database.

[Microbial communities of the discharge zone of oil- and gas-bearing fluids in low-mineral Lake Baikal].

At the site of natural ingress of oil microbial diversity in the Central Baikal bottom sediments differing in the chemical composition of pore waters was studied by molecular biological techniques. The sediments saturated with oil and methane were found to contain members of 10 bacterial and 2 archaeal phyla. The oxidized sediment layer contained methanotrophic bacteria belonging to the Alphaproteobacteria, which had a specific structure of the pmoA gene and clustered together with uncultured methanotrophs from cold ecosystems. The upper sediment layer contained also oil-oxidizing bacteria and the alkB genes most colsely related to those of Rhodococcus. The microbial community of reduced sediments exhibited lower diversity and was represented mostly by the organisms involved in hydrocarbon biodegradation.

[Production of gaseous hydrocarbons by microbial communities of Lake Baikal bottom sediments].

Production of gaseous hydrocarbons by the microbial community of the Posolsky Bank methane seep bottom sediments (Southern Baikal) was studied at 4°C. Formation of both methane and a heavier gas- eous hydrocarbon, ethane, was detected in enrichment cultures. The highest methane concentrations (6.15 and 4.51 mmol L(-1)) were revealed in enrichments from the sediments from 55-cm depth incubated with-so- dium acetate and H2/CO2 gas mixture, respectively. A decrease in activity of aceticlastic methanogensand a decrease in methane concentration produced by hydrogenotrophic archaea occurred with depth. The highest concentration of ethane was revealed in enrichments from the microbial community of the layer close to gas hydrates (75 cm) incubated with CO2 as a substrate. According to analysis of the 16S rRNA gene fragments from the clone library, these enrichments were found to contain members of the phylum Crenarchaeota form- ing a separate cluster with members of the class Thermoprotei. The phylum Euryarchaeota was represented by nucleotide sequences of the organisms homologous to members of the orders Methanococcales, Methanosa- rcinales, and Thermoplasmatales.