[Taxonomic Composition of Lake Baikal Bacterioneuston Communities].

The taxonomic composition of microbial communities of Lake Baikal surface microlayer was studied by pyrosequencing of the 16S rDNA amplicons. Statistically reliable differences were found between bacterioneuston of the shallow and deep-water stations. The shallow station community was characterized by higher diversity than the deep-water one. While bacterioneuston communities were shown to be less diverse than the water column communities, their diversity was comparable to that of other biofilm associations. Microbial communities of Lake Baikal surface microlayer were shown to be similar to those of the water column in the composition of predominant phyla, while differing considerably at the genus level. Bacterioneuston of Lake Baikal was comparable to microbial communities of the surface microlayer of other freshwater basins, although it was characterized by high abundance of the Alphaproteobacteria and Verrucomicrobia. High abundance of photoheterotrophs compared to the water column communities of other freshwater basins was another distinctive feature of Lake Baikal bacterioneuston. Our results showed the Lake Baikal surface microlayer to be a specific microbial community with low species diversity and relatively high abundance of photoheterotrophic microorganisms.

Phylogenetic and Functional Prokaryotic Diversity in the Hoito-Gol Mesothermal Mineral Spring (Eastern Savan Mountains. Buryat Renuhlie).

High-throughput sequencing was used for comparative analysis of microbial communities of the water and mat from the Hoito-Gol mesothermal mineral sulfide spring (Eastern Sayan Mountains, Buryat Republic). Activity of microbial communities was determined. While both spring biotopes were dominated by members of three bacterial phyla, Proteobacteria, Bacteroidetes, and Firmicutes, they differed drastically in the composition of predominant phylotypes (at the genus level). In the water, the organisms wide spread in aquatic'environments were predominant, mostly aerobic chemoorganotrophs of the generaAcinetobacter, Pe- dobacter, and Flavobacterium. In the microbial mat,;the organisms actively involved in the sulfur cycle predominated, including sulfur-reducing bacteria Sulfurospirillum, sulfate-reducing deltaproteobacteria, sulfur- oxidizing chemoautotrophic bacteria, anoxygenic phototrophic bacteria of,the phyla Chloroflexi and Chloro- bi, as well as purple bacteria belonging to the Q-, P--, and y-Proteobacteria. Microbial mats of the spring exhibited higher phylogenetic diversity compared to high-temperature mats containing photosynthetic microorganisms.

[Diversity and Physiological and Biochemical Properties of Heterotrophic Bacteria. Isolated from Lake Baikal Neuston.]

For heterotrophic microorganisms (44 strains) isolated-from the surface film of Lake Baikal, iden- tification was carried out and their. physiological and biochemical characteristics were determined. Com- pared to the water column, diversity of cultured heterotrophs was low, indicating formation of stable micro- bial communities at the air-water interphase interface. Heterotrophic bacteria isolated from the surface mi- crolayer exhibited the enzymatic activity comparable to that for strains form other biofilm associations. Deinococcusfi6us strain NA202 'vas the most active component of the community, capable of utilization of the broadest spectrum of mono- and disaccharides,'sugars, and amino acids. This strain possessed the highest diversity of extracellular enzymes and was the most resistant to UV radiation. The physiological and bio- chemical properties of this strain may-be responsible for its adaptation to survival in extreme conditions of the surface microlayer. Our results improve our understanding of occurrence of UV-resistant strains in freshwater ecosystems.

[Study of the Microbiome of the Intestine of the Comephorus dybowski Korotneff, 1904].

Data on metagenomic analysis of the microbial community of the intestine of the Comephorus dybowski are presented for the first time. It was established that the bacterial community is characterized by a significant species diversity. In its composition 301 phylotypes (OTU) belonging to 23 phyla (out of which six are candidate, including the Thermobaculum, Gracilibacteria, Candidatus Saccharibacteria, TM6, Latescibacteria, and Parcubacteria) were detected. It was demonstrated that species richness estimated by means of the non-parametric ACE and Chao1 criteria was 568 and 504, respectively; and the species diversity by the Shannon index was 4.05. The analysis ofunique peculiarities of the C. dybowski ecology and biology allows us to explain some of the data obtained on the intestinal microbiome of this specie.

[Phylogenetic analysis of bacteria of extreme ecosystems].

Phylogenetic analysis of aerobic chemoorganotrophic bacteria of the two extreme regions (Dead Sea and West Antarctic) was performed on the basis of the nucleotide sequences of the 16S rRNA gene. Thermotolerant and halotolerant spore-forming bacteria 7t1 and 7t3 of terrestrial ecosystems Dead Sea identified as Bacillus licheniformis and B. subtilis subsp. subtilis, respectively. Taking into account remote location of thermotolerant strain 6t1 from closely related strains in the cluster Staphylococcus, 6t1 strain can be regarded as Staphylococcus sp. In terrestrial ecosystems, Galindez Island (Antarctic) detected taxonomically diverse psychrotolerant bacteria. From ornithogenic soil were isolated Micrococcus luteus O-1 and Microbacterium trichothecenolyticum O-3. Strains 4r5, 5r5 and 40r5, isolated from grass and lichens, can be referred to the genus Frondihabitans. These strains are taxonomically and ecologically isolated and on the tree diagram form the joint cluster with three isolates Frondihabitans sp., isolated from the lichen Austrian Alps, and psychrotolerant associated with plants F. cladoniiphilus CafT13(T). Isolates from black lichen in the different stationary observation points on the south side of a vertical cliff identified as: Rhodococcus fascians 181n3, Sporosarcina aquimarina O-7, Staphylococcus sp. 0-10. From orange biofilm of fouling on top of the vertical cliff isolated Arthrobacter sp. 28r5g1, from the moss-- Serratia sp. 6r1g. According to the results, Frondihabitans strains most frequently encountered among chemoorganotrophic aerobic bacteria in the Antarctic phytocenoses.

[Molecular-genetic detection of a nonpathogenic genotype of Spironucleus barkhanus (Diplomonadida: Hexamitidae) in the black Baikal grayling (Thymallus arcticus baicalensis Dybowski, 1874)].

A nonpathogenic genotype of Spironucleus barkhanus (Diplomonadida: Hexamitidae) has been revealed for the first time in the Baikal grayling (Salmoniformes: Thymallidae) by molecular-genetic methods. Sequences corresponding to a fragment of the gene encoding the small ribosomal subunit RNA (SSU rRNA) have been obtained. The genotype of S. barkhanus from Baikal fish is identical to that characteristic of the parasite found in freshwater salmonid fishes.

[Spatial distribution and species composition of prosthecate bacteria in Lake Baikal].

From the water column of Lake Baikal, several strains of prosthecate bacteria belonging to the genera Caulobacter and Brevundimonas were isolated. In this article, the methods applied for their isolation and cell number determination are described; the occurrence frequency and spatial distribution of these microorganisms in the lake are demonstrated. Characterization of the species composition of cultivable and uncultivable prosthecate bacteria was carried out using the methods of traditional and molecular microbiology, respectively. A comparative phylogenetic analysis of the DNA sequences of uncultivable bacteria, which showed homology to the members of the alpha subclass of proteobacteria, was carried out. It was demonstrated that the lake water column is inhabited by uncultivable alpha-proteobacteria of uncertain phylogenetic affinity, in addition to representatives of the species Caulobacter vibrioides and C. leidyi, which were detected by traditional microbiological methods.

[Biodiversity and activity of the microbial community in the Kotelnikovsky Hot Springs (Lake Baikal)].

Complex microbiological and chemical analyses of water and bacterial mats were performed in the Kotelnikovsky Hot Springs (Lake Baikal). Transmission electron microscopy demonstrated that short rods about 1.2-2 microm in diameter predominated in the natural microbial community. Scanning electron microscopy coupled with chemical analysis revealed a characteristic P peak in the bacteria-like mineral particles, which suggests their biogenic origin. Most strains of the thermophilic microorganisms were gram-positive spore-forming rods and can be assigned to the genus Bacillus. Assays for potential enzyme activity demonstrated that most of the strains tested were active at high temperature. The data obtained suggest high activity of the bacterial community in situ and its particular role in the functioning of the hydrothermal ecosystem.

[Microbial biodiversity in the Lake Baikal water]. / Kharacteristika bioraznoobraziia mikrobnogo soobshchestva vodnoi tolshchi ozera Baikal.

The investigation of the microbial community of Lake Baikal by the methods of general and molecular microbiology showed that culturable bacterial strains were represented by various known genera. The lake water contains a great number of bacterial morphotypes, as revealed by electron microscopy, and a great diversity of nonculturable microorganisms belonging to different phylogenetic groups, as revealed by 16S rRNA gene fragment sequencing. The inference is made that the microbial community of Lake Baikal contains not only the known species but also new, possibly endemic to the lake, bacterial species.

[The detection of cyanobacterial cells by a non-fluorescent in situ hybridization method]. / Primenenie metoda gibridizatsii in situ dlia vyiavleniia tsianobakterial'nykh kletok.

Seven cyanobacterial strains (Anabaena macrospora NIER10016, Oscillatoria sp. NIER10042, Microcystis aeruginosa NIER10015, M. ichtyoblabe NIER10025 and NIER10040, M. novacekii NIER10029, and M. wesenbergii NIER10068) were tested by a non-fluorescent in situ hybridization method using two specific horseradish peroxidase--labeled oligonucleotide probes and two chromogenic substrates. This approach was shown to be appropriate for analysis of natural samples.

[Diversity of bacteria at various depths in the southern part of lake Baikal as detected by 16S rRNA sequencing]. / Bioraznoobrazie bakterii na razlichnykh glubinakh iuzhnoi kotloviny ozera Baikal, vyiavlennoe po posledovatel'nostiam 16S rRNK.

Phylogenetic analysis of the bacterial community inhabiting the water of Lake Baikal was performed on the basis of 16S rRNA sequencing. The composition of the bacterial community was shown to vary significantly with depth. Cyanobacteria were dominant species at the surface of the lake. At a moderate depth (400 m), actinomycete relatives were most abundant. At a great depth and near the bottom, the community was composed mainly of proteobacteria and cyanobacteria (the latter are probably brought from the surface layers by vertical near-shore water fluxes). Most of the bacterial 16S rRNA sequences detected exhibited low similarity to those known and formed separate clusters in the phylogenetic tree, which may indicate the endemic nature of the corresponding bacteria.