Microbial community structure in methane hydrate-bearing sediments of freshwater Lake Baikal

Abstract

Gas hydrates in marine sediments have been known for many years but recently hydrates were found in the sediments of Lake Baikal, the largest freshwater basin in the world. Marine gas hydrates are associated with complex microbial communities involved in methanogenesis, methane oxidation, sulfate reduction and other biotransformations. However, the contribution of microorganisms to the formation of gas hydrates remains poorly understood. We examined the microbial communities in the hydrate-bearing sediments and water column of Lake Baikal using pyrosequencing of 16S rRNA genes. Aerobic methanotrophic bacteria dominated the water sample collected at the lake floor in the hydrate-bearing site. The shallow sediments were dominated by Archaea. Methanogens of the orders Methanomicrobiales and Methanosarcinales were abundant, whereas representatives of archaeal lineages known to perform anaerobic oxidation of methane, as well as sulfate-reducing bacteria, were not found. Affiliation of archaea to methanogenic rather than methane-oxidizing lineages was supported by analysis of the sequences of the methyl coenzyme M reductase gene. The deeper sediments located at 85-90 cm depth close to the hydrate were dominated by Bacteria, mostly assigned to Chloroflexi, candidate division JS1 and Caldiserica. Overall, our results are consistent with the biological origin of methane hydrates in Lake Baikal.

Shifts among Eukaryota, Bacteria, and Archaea define the vertical organization of a lake sediment

“…The Dehalococcoidales (Chloroflexi [65, 66]) and the Miscellaneous Crenarchaeotic Group (MCG, [67, 68]) are promising candidates for such hybrid forms of energy harvesting and were among the most influential lineages in our data set (Additional file 4). The MCG co-occurred with Dehalococcoidales, similar to what was found in methane hydrate-bearing sediment in Lake Baikal at >1500-m water depth [69]. Another indication that biotic interactions are important in Lake Stechlin sediments is the appearance of the Candidatus Parvarchaeum as a structuring lineage (Fig.…”

The Structure of Microbial Community and Degradation of Diatoms in the Deep Near-Bottom Layer of Lake Baikal

“…Metagenomic analysis [39] has been used to evaluate the diversity of microorganisms in marine ecosystems [40]–[44], thermal springs [45], [46], and fresh water bodies [47], including sites with gas hydrate-bearing sediments in Lake Baikal [48].…”

Substratum‐Associated Microbiota

“…Community structure of bacteria, archaea and viruses, in the deep and anoxic sediments of the volcanic Lake Pavin (France) gradually changed with depth and some showed exceptional morphotypes . The microbial assemblages in the hydratebearing sediments of Lake Baikal showed that shallow sediments were dominated by Archaea, deeper sediments located at 8590 cm depth close to the hydrate were dominated by bacteria, consistent with the biological origin of methane hydrates in Lake Baikal (Kadnikov et al, 2012). The examination of Acidobacteria in freshwater ponds at Doana National Park (southwestern Spain) showed that in oxygen-saturated areas in the sediment surface, around 4% of total bacterial RNA belonged to Acidobacteria (Zimmermann et al, 2012).…”