Search

A collection of heterotrophic bacteria consisting of 167 strains was obtained from microbial communities of biofilms formed on solid substrates in the littoral zone of Lake Baikal. Based on the analysis of 16S rRNA gene fragments, the isolates were classified to four phyla: Proteobacteria , Firmicutes , Actinobacteria , and Bacteroidetes . To assess their biotechnological potential, bacteria were screened for the presence of PKS (polyketide synthase) and NRPS (non-ribosomal peptide synthetases) genes. PKS genes were detected in 41 strains (25%) and NRPS genes in 73 (43%) strains by PCR analysis. The occurrence of PKS genes in members of the phylum Firmicutes (the genera Bacillus and Paenibacillus ) was 34% and NRPS genes were found in 78%. In Proteobacteria , PKS and NRPS genes were found in 20% and 32%, and in 22% and 22% of Actinobacteria , respectively. For further analysis of PKS and NRPS genes, six Bacillus and Paenibacillus strains with antagonistic activity were selected and underwent phylogenetic analysis of 16S rRNA genes. The identification of PKS and NRPS genes in the strains investigated was demonstrated among the homologues the genes involved in the biosynthesis of antibiotics (bacillaene, difficidine, erythromycin, bacitracin, tridecaptin, and fusaricidin), biosurfactants (iturin, bacillomycin, plipastatin, fengycin, and surfactin) and antitumor agents (epothilone, calyculin, and briostatin). Bacillus spp. 9A and 2A strains showed the highest diversity of PKS and NRPS genes. Bacillus and Paenibacillus strains isolated from epilithic biofilms in Lake Baikal are potential producers of antimicrobial compounds and may be of practical interest for biotechnological purposes., A collection of heterotrophic bacteria consisting of 167 strains was obtained from microbial communities of biofilms formed on solid substrates in the littoral zone of Lake Baikal. Based on the analysis of 16S rRNA gene fragments, the isolates were classified to four phyla: Proteobacteria , Firmicutes , Actinobacteria , and Bacteroidetes . To assess their biotechnological potential, bacteria were screened for the presence of PKS (polyketide synthase) and NRPS (non-ribosomal peptide synthetases) genes. PKS genes were detected in 41 strains (25%) and NRPS genes in 73 (43%) strains by PCR analysis. The occurrence of PKS genes in members of the phylum Firmicutes (the genera Bacillus and Paenibacillus ) was 34% and NRPS genes were found in 78%. In Proteobacteria , PKS and NRPS genes were found in 20% and 32%, and in 22% and 22% of Actinobacteria , respectively. For further analysis of PKS and NRPS genes, six Bacillus and Paenibacillus strains with antagonistic activity were selected and underwent phylogenetic analysis of 16S rRNA genes. The identification of PKS and NRPS genes in the strains investigated was demonstrated among the homologues the genes involved in the biosynthesis of antibiotics (bacillaene, difficidine, erythromycin, bacitracin, tridecaptin, and fusaricidin), biosurfactants (iturin, bacillomycin, plipastatin, fengycin, and surfactin) and antitumor agents (epothilone, calyculin, and briostatin). Bacillus spp. 9A and 2A strains showed the highest diversity of PKS and NRPS genes. Bacillus and Paenibacillus strains isolated from epilithic biofilms in Lake Baikal are potential producers of antimicrobial compounds and may be of practical interest for biotechnological purposes., (© 2018 Elena Sukhanova et al.)

Denitrification is the major process of nitrate reduction to dinitrogen (N2). This is the first report on detection of the nirK type denitrifying bacteria in the epilithic biofilms of the Lake Baikal littoral zone. The highest species diversity was revealed in microbial communities of the biofilms collected in the area of the Bol'shoe Goloustnoe settlement and Severobaikal'sk City, while those collected in the vicinity of Listvyanka settlement exhibited the lowest diversity. Phylogenetic analysis showed uncultured denitrifying bacteria from diverse habitats were most closely related to all cloned sequences. The closely related homologs were represented by the sequences of the orders Rhizobiales and Rhodobacterales, class Alphaproteobacteria. [ABSTRACT FROM AUTHOR]

This article presents the results of research into autochthonous bacteriophages, a previously unknown element in the structure of the microbial loop in the ecosystem of deep oligotrophic Lake Baikal. Transmission electron microscopy was used to study the morphological diversity of phages in the water column, surface microlayer, and benthic biofilms formed at the interface between water and geological rocks (marble, granite, mica, quartz, amphibolite, gabbro, and urtite). This article presents data on the dimensional structure of autochthonous bacteriophages, as well as their quantity, seasonal dynamics, and vertical distribution from the surface to the maximum depth (1200 m) when compared with the content of bacteria. Several morphotypes of Baikal autochthonous bacteriophages affecting Pseudomonas aeruginosa have been isolated and characterized by molecular-genetic methods. The complete genomes of giant phage PaBG from the Myoviridae family and phage MD8 from the Siphoviridae family have been determined. [ABSTRACT FROM AUTHOR]

Bacterial communities of the water and the biofilm formed during five years on an artificial substrate in Lake Baikal were studied by the pyrosequencing of 16S rRNA gene fragments; taxonomic diversity of bacterial communities and differences in their structure were revealed. The biofilm community contained mainly representatives of three phyla: Cyanobacteria, Bacteroidetes, and Proteobacteria; the amounts of other groups were within 1%. Bacterial community of the plankton was more heterogeneous; along with the dominant phyla ( Bacteroidetes, Actinobacteria, and Proteobacteria) 15% of the members were of the other phyla. The use of pyrosequencing allowed to reveal 35 bacterial phyla in Lake Baikal, some of which were identified for the first time; moreover, minor groups of microorganisms (including only several sequences), which were not earlier determined by other molecular methods were found. [ABSTRACT FROM AUTHOR]