The robustness of the trees was estimated by posterior probabilities. The nucleotide sequences reported in this paper have been PFT�� datasheet submitted to GenBank (FJ798929–FJ798951; GU256228–GU256245). The abundances of picoplanktonic cyanobacteria and heterotrophic bacteria were different in the lake basins in early June, 2008. In Northern Baikal picoplanktonic

cyanobacteria of the genera Synechococcus, Cyanobium and Synechocystis developed in huge numbers. They were dominated by an endemic Baikalian autotrophic picoplankton species –Synechocystis limnetica, which constituted 20% of the total picocyanobacterial number at depths of 0–25 m. As a whole, the numbers of picocyanobacteria reached 268 000 cells mL−1 at a depth of 5 m; the abundance of heterotrophic bacteria was about 288 000 cells mL−1 in the upper 25-m layer (Fig. 1). Thus, the share of picocyanobacteria in the total bacterial plankton number was about 50%, in biomass – 68%. At this time, the development of autotrophic picoplankton in Southern Baikal was low, and the numbers of picocyanobacteria were 12 400 cells mL−1 in the 0–25-m layer (Fig. 1). The main components of picocyanobacteria communities were species of Synechococcus

and Cyanobium genera, but, in contrast to the Northern basin, the contribution of S. limnetica to the total abundance did not exceed 4%. The abundance of bacteria in the Southern basin was high and averaged 1 780 000 mL−1 BCKDHA in the 0–25-m layer Palbociclib solubility dmso (Fig. 1). The share of the picocyanobacteria in total bacterial plankton abundance was only 1%,

in biomass – 3%. PCR products were obtained from both Northern and Southern Baikal water samples: each sample exhibited five bands that approximately ranged from 350 to 500 bp. All five bands of g23 amplicons from Northern Baikal water samples and only three bands from Southern Baikal were successfully reamplified. We constructed clone libraries of the purified g23 gene PCR products obtained from two stations. The recovery efficiency of g23 gene fragments from Southern Baikal was lower and only 70% of the clones contained correct g23 inserts within this clone library. In total, 23 clones from Northern Baikal and 18 from Southern Baikal were sequenced and translated (g23 amino acid sequence from 118 to 289 in the coliphage T4 sequence, Parker et al., 1984). The predicted amino acid sequences from Lake Baikal were variable in length from 105 to 143 residues. Each clone was designated as N0508 (Northern Baikal clone library) or S0508 (Southern Baikal), followed by band and clone numbers. The most similar based on blast hits were the g23 clones from marine, paddy fields and T4 cyanophages (from 70% and higher). The highest identity was observed between S0508/2-4 clone and CS26 marine clone (89%) (Fig. 2). Two highly conserved amino acid motifs of g23 marine sequences uncovered by Filée et al.