Production of Gaseous Hydrocarbons by Microbial Communities of Lake Baikal Bottom Sediments

摘要

Production of gaseous hydrocarbons by the microbial community of the Posolsky Bank methane seep bottom sediments (southern Baikal) was studied at 4°C. Formation of both methane and a heavier gaseous hydrocarbon, ethane, was detected in enrichment cultures. The highest methane concentrations (6.15 and 4.51 mmol L~(–1)) were revealed in enrichments from the sediments from 55-cm depth incubated with sodium acetate and H_2/CO_2 gas mixture, respectively. A decrease in activity of aceticlastic methanogens and a decrease in methane concentration produced by hydrogenotrophic archaea occurred with depth.The high-est concentration of ethane was revealed in enrichments from the microbial community of the layer close to gas hydrates (75 cm) incubated with CO_2 as a substrate. According to analysis of the 16S rRNA gene frag-ments from the clone library, these enrichments were found to contain members of the phylum Crenarchaeota forming a separate cluster with members of the class Thermoprotei. The phylum Euryarchaeota was repre-sented by nucleotide sequences of the organisms homologous to members of the orders Methanococcales, Methanosarcinales, and Thermoplasmatales.