Abstract
Methanogenic archaea produce methane as a metabolic product under anoxic conditions and they play a crucial role in the global methane cycle. In this study molecular diversity of methanogenic archaea in the hyporheic sediment of the lowland stream Sitka (Olomouc, Czech Republic) was analyzed by PCR amplification, cloning and sequencing analysis of the methyl coenzyme M reductase alpha subunit (mcrA) gene. Sequencing analysis of 60 clones revealed 24 different mcrA phylotypes from hyporheic sedimentary layers to a depth of 50 cm. Phylotypes were affiliated with Methanomicrobiales, Methanosarcinales and Methanobacteriales orders. Only one phylotype remains unclassified. The majority of the phylotypes showed higher affiliation with uncultured methanogens than with known methanogenic species. The presence of relatively rich assemblage of methanogenic archaea confirmed that methanogens may be an important component of hyporheic microbial communities and may affect CH4 cycling in rivers.
Highlights
The decomposition of organic matter in aquatic sediments is an important process in global and local carbon budgets, as it recycles complex organic compounds from terrestrial and aquatic environments into carbon dioxide and methane
Methanogenic archaea belonging to the Euryarchaeota phylum are divided into seven orders: Methanopyrales, Methanococcales, Methanobacteriales, Methanomicrobiales, Methanosarcinales and the recently recognized groups Methanocellales and Methanoplasmatales [10,11]
Ferric iron is reduced to ferrous iron in anoxic conditions by bacteria which utilize this reduction process for their growth
Summary
The decomposition of organic matter in aquatic sediments is an important process in global and local carbon budgets, as it recycles complex organic compounds from terrestrial and aquatic environments into carbon dioxide and methane. The latter is a major component in the carbon cycle of anaerobic aquatic systems. Since a relatively large amount of methane production has been observed in river sediments [1,2,3,4], we hypothesised that river sediments may act as a considerable source of methane gas emission into the environment [5]. Methanogenic archaea are ubiquitous in anoxic environments and require a redox potential of less than -300
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