[Comparative characteristics of microbial communities in two regions of natural oil seepage in Lake Baikal].

Microbial communities and hydrocarbon contents have been studied in two regions of natural oil seepage in Lake Baikal: (1) opposite the Bol'shaya Zelenovskaya River mouth (studied previously) and (2) near Cape Gorevoi Utes (discovered in 2005). The abundance of both heterotrophic and hydrocarbon-oxidizing microorganisms is significantly higher in water samples from the first region, where the oil is biologically degraded. In the surface soil layer at stations located in the immediate vicinity of oil seepage site, the abundance of n-alkane-oxidizing microorganisms reaches 2000 cells/ml, and that of oil-oxidizing microorganisms reaches 2600 cells/ml. In water samples from near Cape Gorevoi Utes, the abundance of these groups of microorganisms does not exceed 190 and 500 cells/ml, respectively.

[Microbial community of freshwater sponges in Lake Baikal].

The microbial community of Baikal sponges has been studied in five species belonging to the genera Swartschewskia, Baicalospongia, and Lubomirskia of the endemic family Lubomirskiidae. The results show that the total numbers of bacteria and bacterioplankton production have an effect on the growth of L. baicalensis body. Bacteria of the genera Pseudomonas, Bacillus, Micrococcus, Sarcina, Flavobacterium, Arthrobacter, and Acinetobacter living in the sponges are representatives of the Baikal bacterioplankton. Actinomycetes of the genera Streptomyces and Micromonospora are a permanent component of the cultivable sponge microbial community. The numbers and enzyme activities of heterotrophic, oligotrophic, and psychrophilic bacteria isolated from different sponge species and the surrounding water in autumn and in winter have been estimated.

[Comparative molecular biological analysis of the microbial community of the holocene and pleistocene deposits of Posol'skaya Shoal, Lake Baikal].

The bacterial diversity was studied in sediment layers of Posol'skaya Shoal station (Southern Baikal) belonging to different periods. A set of primers specific to individual bacterial groups was used to analyze the 16S rRNA gene fragments. The bacterial diversity in the Holocene deposits was found to be higher than in the Pleistocene ones. In the upper sediments, a positive PCR reaction with bacterial primers and with specific cyanobacterial and archaebacterial primers was detected. The following phylogenetic groups were revealed in the microbial community of the surface horizon: green nonsulfur bacteria, delta-proteobacteria, beta-proteobacteria (Nitrospirae), alpha-proteobacteria, acidobacteria, crenarchaeota, euryarchaeota, and groups of uncultured bacteria. From the DNA of the Pleistocene deposits, the PCR product was obtained only with bacterial primers. The representatives of the genus Pseudomonas were most closely related to the sequences obtained (95-97% homology).

[The biodiversity of actinomycetes in Lake Baikal]. / K voprosu o bioraznoobrazii aktinomitsetov v ozere Baikal.

The taxonomic analysis of 107 actinomycete strains isolated from the bottom sediments and water of Lake Baikal showed that most of the water isolates belong to the genus Streptomyces and most of the sediment isolates belong to the genus Micromonospora. In the sediments, the number of actinomycetes increased with depth (down to 200 m). Eight Streptomyces isolates were identified to a species level.

[On the vertical distribution of microorganisms in lake Baikal during spring deep-water renewal]. / O vertikal'nom raspredelenii mikroorganizmov v ozere Baikal v period vesennego obnovleniia glubinnykh vod.

The vertical distribution of microorganisms during spring deep-water renewal in Lake Baikal was studied. The downward advection of trophogenic waters was found to create conditions for the extensive growth of microorganisms capable of decomposing and mineralizing organic carbon, nitrogen, and phosphorus in deep water layers. These processes occur annually at spring thermal bars near the underwater slope of Lake Baikal, whereas in its pelagic zone, the deep intrusions of waters rich in organic material are observed only in the years when enhanced deep-water renewal is accompanied by a high spring yield of phytoplankton.