Bacterial methanogenesis in soda lakes of the southeastern Transbaikal region

Data are presented on the activity of hydrogenotrophic, methylotrophic, and acetotrophic methanogenic bacteria in bottom sediments and microbial mars of alkaline lakes in the southeastern Transbaikal region. The rate of overall methanogenesis in the sediments was 0.14-6.01 mu l CH4/l per day, whereas, in microbial mats, it ranged from to 0.06 to 8.17 mu l CH4/l per day. Hydrogenotrophic and methylotrophic methanogenic bacteria were the most active in methane production (50-99 and 0.5-97%, respectively, of the total amount of methane produced), whereas acetate-catabolizing methanogens produced only 0.2-4% of the total methane. As compared to sulfate-reducing bacteria, methanogenic bacteria were of secondary importance in the degradation of organic compounds in the low-salt soda lakes studied: methanogens utilized from 0.035 to 3.02 mu g C/l per day, which was by 3 to 4 orders of magnitude lower than the activity of sulfate-reducing bacteria. Daily methane production in the sediments studied was 3.4-30 mu g CH4/m(2).