Distribution and diversity of sulfate-reducing bacteria in weakly mineralized alkaline hydrotherms of Baikal rift zone

Weakly mineralized alkaline hydrotherms of the Baikal Rift Zone (BRZ) create favourable conditions for the development of thermophilic and mesophilic sulfate-reducing bacteria. We have studied the diversity and distribution of sulfate reducers using cultural and molecular approaches. The sulfidogenic community is represented by bacteria of the classes Nitrospira, Deltaproteobacteria, Clostridia and Thermodesulfobacteria. These are numerous thermophilic bacteria of Thermodesulfovibrio genus (class Nitrospira) and mesophilic bacteria of Desulfarculus genus (class Deltaproteobacteria), rare bacteria of Desulfobacca, Desulfococcus (class Deltaproteobacteria), Desulfotomaculum, Thermodesulfobium, Desulfurispora (class Clostridia) genera. In the alkaline conditions of thermal springs thermophilic and mesophilic sulfate-reducing bacteria participate in the reducing phase of the sulfur cycle in the pH range from 7 to 10,5 and temperatures from 30 to 75 °С. The data obtained indicate that numerous and rare SRB taxa can occupy different ecological niches and together maintain the ecological significance of sulfate-reducing bacteria in alkaline hydrotherms of the BRZ.