Identification of microbial communities involved in the methane cycle of a freshwater meromictic lake

Abstract

Editor: Gary KingKeywords a-subunit of the particulate methane monooxygenase; a-subunit of the methylcoenzyme M reductase; aerobic methanotrophy; methanogenesis. AbstractLake Pavin is a meromictic crater lake located in the French Massif Central area. In this ecosystem, most methane (CH 4 ) produced in high quantity in the anoxic bottom layers, and especially in sediments, is consumed in the water column, with only a small fraction of annual production reaching the atmosphere. This study assessed the diversity of methanogenic and methanotrophic populations along the water column and in sediments using PCR and reverse transcription-PCR-based approaches targeting functional genes, i.e. pmoA (a-subunit of the particulate methane monooxygenase) for methanotrophy and mcrA (a-subunit of the methylcoenzyme M reductase) for methanogenesis as well as the phylogenetic 16S rRNA genes. Although methanogenesis rates were much higher in sediments, our results confirm that CH 4 production also occurs in the water column where methanogens were almost exclusively composed of hydrogenotrophic methanogens, whereas both hydrogenotrophs and acetotrophs were almost equivalent in the sediments. Sequence analysis of markers, pmoA and the 16S rRNA gene, suggested that Methylobacter may be an important group actively involved in CH 4 oxidation in the water column. Two main phylotypes were characterized, one of which could consume CH 4 under conditions where the oxygen amount is undetectable.

Illuminating Microbial Dark Matter in Meromictic Sakinaw Lake

“…As O 2 concentrations decrease below 33 m, Proteobacteria abundance increases, consistent with patterns observed in other meromictic lake ecosystems (17,45,(52)(53)(54). At depths between 33 and 36 m, where concentrations of SO 4 2Ϫ , Fe, and Mn are at their highest, OTUs affiliated with putative sulfatereducing Deltaproteobacteria are abundant.…”

Unexpected and novel putative viruses in the sediments of a deep-dark permanently anoxic freshwater habitat

“…The infected hosts exhibited sheath and flat ends (Supplementary Figure S2c), similar to those typical of the methanogenic species M. concilii (Supplementary Figure S2d) (Patel and Sprott, 1990). Even if there is no certitude about the identity of the infected cell, its tentative affiliation to Methanosaeta, in addition to the morphological similarities, is supported by the data on the occurrence of members of this genus as a dominant archaeal group in the sediments of Lake Pavin (Lehours et al, 2007;Biderre-Petit et al, 2011). Methanosaeta genus is known to be widely distributed in different environments and is probably the predominant methane producer on earth (Smith and Ingram-Smith, 2007).…”

Methanogenic System of a Small Lowland Stream Sitka, Czech Republic

“…Our results from the DGGE analysis are supported by cloning and sequencing of methyl coenzyme M reductase (mcrA) gene which also retrieved relatively rich diversity (25 different mcrA gene clones) of the methanogenic community in the Sitka stream hyporheic sediments. Similar richness in number of clones was also mentioned in a methanogenic community in Zoige wetland, where 21 different clones were found (Zhang et al 2008a), while 20 clones were described in the methane cycle of a meromictic lake in France (Biderre-Petit et al 2011). In addition, soils from Ljubljana marsh (Slovenia) showed 17 clones (Jerman et al 2009), for example.…”