Interconnection of bacterial and phytoplanktonic communities with hydrochemical parameters from ice and under-ice water in coastal zone of Lake Baikal.

We analysed the relationship between the chemical complex (concentration of dissolved ions, nutrients, pH) and biological parameters (primary production, biomass of phytoplankton, abundance and activity of bacterial communities) at estuaries of rivers and coastal waters of Southern Baikal during the under-ice period. Correlation network analysis revealed CO2 to be the main limiting factor for the development of algae and microbial communities in the coastal zone of Lake Baikal. This study indicates that primarily reverse synthesis of bicarbonate and carbonate ions associated with the development of phytoplankton and accumulation of dissolved CO2 during photosynthesis regulates pH in the Baikal water. We did not detect the anthropogenic factors that influence the change in pH and acidification. Near the Listvyanka settlement (Lake Baikal, Listvennichnaya Bay), there was a great number of organotrophs and thermotolerant bacteria with low bacterioplankton activity and high concentration of organic carbon. This evidences eutrophication due to the influx of organic matter having an anthropogenic source. Nutrients produced during the bacterial destruction of this matter may explain the changes in bottom phytocenoses of Listvennichnaya Bay.

[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.

[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 first results of a study of the phylogenetic diversity of microorganisms in southern Baikal sediments from the area of subsurface depositions of methane hydrates].

Phylogenetic analysis of the bacterial communities in Lake Baikal bottom sediments in the region of subsurface methane hydrate depositions has been carried out using data on 16S rRNA sequences. The composition of these microbial communities is shown to be different in different horizons. Methanotrophic bacteria are found in the surface layer (0-5 cm), and uncultured bacteria constitute a great portion of this population. In deeper sediment layers (92-96 cm), achange in the microbial community occurs; specifically, a decreased homology with the known sequences is observed. The new sequences form separate clusters on a phylogenetic tree, indicating the possibly endemic nature of the bacteria revealed. Organisms related to the genus Pseudomonas constitute the main portion of the population. An archaea-related sequence was found in a horizon containing gas hydrate crystals (100-128 cm). Uncultured bacteria remain predominant.