Diversity of Denitrifying Bacteria in Biofilms Formed on Stony Substrates of the Lake Baikal Littoral Zone

Denitrification is the major process of nitrate reduction to dinitrogen (N-2). 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.