Anaerobic oxidation of methane in differences types of geological structures at Lake Baikal

Abstract

Although in sediments of Lake Baikal process of anaerobic oxidation methane was revealed by radioisotope techniques, by of the methane profile we know a little about the microorganisms carrying out this process. Here we studied diversity of archaeal communities in different types geological structures (methane seeps and mud volcano) on Lake Baikal with different composition of pore waters and the discharged fluid. In investigate were used different methods molecular biology including of high-throughput sequencing of gene 16S rRNA and PCR analysis different genes of AOM (mcrA). Molecular analysis did not reveal methane-oxidizing archaea ANME-1, -2, or -3, which are responsible for anaerobic oxidation of methane in marine sediments. Hydrogenotrophic methanogenic archaea representatives of the orders Methanomicrobiales, Methanococcales, as well as acetoclastic methanogens of the order Methanosarsinales were abundant in a mud volcano at Lake Baikal. In investigation sites we found divers M. nitroreducens-like archaea (ANME-2d subcluster) both in deep sediments of a methane seeps and in a mud volcanoes. Their closest homologues involved in process anaerobic oxidation of methane in different freshwater systems, bioreactors, paddy field soils.

Molecular Indicators of Sources and Biodegradation of Organic Matter in Sediments of Fluid Discharge Zones of Lake Baikal

“…Methane and its homologues associated with gas hydrates of the MV Kedr have a thermogenic or secondary-microbial genesis that differs from the other hydrate-bearing zones of the lake due to the active biodegradation processes. These data are consistent with the presence of molecular markers of anaerobic methanotrophic archaea in sediments [49].…”

“…The study of the southern basin included the sampling of sediments from the mud volcano Malenky (site 13, Figure 1, Table 1; [6,7,13,28,[48][49][50]) and gas hydrate-bearing sediments from the mud volcano Kedr (site 14, 15, Figure 1, Table 1; [49,51,52]). The former study of gas fluid from the MV Malenky [6] has suggested its possible migration from the deep strata.…”

“…One more sediment core from the southern basin of the lake is located to the south of the Selenga river delta (site 12, Figure 1; Table 1) in the region of the gas hydrate mound (Posolsky Canyon-1; [47]) near the Posolsk Bank where methane seeps and gas hydrates were detected [3,7,13,17,49,50,[53][54][55]. According to the studies of the focused fluid discharge zone in this area, methane has a mixed thermogenic-microbial origin [7].…”

“…The detected archaea genus Methanoperedenaceae (ANME 2d) and bacterial phylum Methylomirabilota (NC10) are the most possible microbes for the aerobic methane oxidation in this and other regions of Lake Baikal. This process is often accompanied by nitrate, nitrite, Fe(III) or Mn (IV) reduction [49].…”

“…The study of OM and hydrocarbon molecular proxies in sediment cores with layers containing authigenic carbonates (Kukuy, site 11; Kedr, site 14,15) gives a new way to understand the conditions of their formation in the specific environment of Lake Baikal. According to the present conception [9,49,51,120,121], the formation of authigenic carbonates of Lake Baikal is associated with microbial methane generation processes. Acetoclastic methanogenesis is one of the most probable processes of methane formation in anaerobic conditions of freshwater reservoirs, but it shows less evidence in Lake Baikal sediments than the hydrogenotrophic way.…”