Abstract
Anaerobic archaeal methanogens are key players in the global carbon cycle due to their role in the final stages of organic matter decomposition in anaerobic environments such as wetland sediments. Here we present the first draft metagenome-assembled genome (MAG) sequence of an unclassified Methanosarcinaceae methanogen phylogenetically placed adjacent to the Methanolobus and Methanomethylovorans genera that appears to be a distinct genus and species. The genome is derived from sediments of a hypersaline (97–148 ppt chloride) unrestored industrial saltern that has been observed to be a significant methane source. The source sediment is more saline than previous sources of Methanolobus and Methanomethylovorans. We propose a new genus name, Methanosalis, to house this genome, which we designate with the strain name SBSPR1A. The MAG was binned with CONCOCT and then improved via scaffold extension and reassembly. The genome contains pathways for methylotrophic methanogenesis from trimethylamine and dimethylamine, as well as genes for the synthesis and transport of compatible solutes. Some genes involved in acetoclastic and hydrogenotrophic methanogenesis are present, but those pathways appear incomplete in the genome. The MAG was more abundant in two former industrial salterns than in a nearby reference wetland and a restored wetland, both of which have much lower salinity levels, as well as significantly lower methane emissions than the salterns.
Highlights
Methanogens play a key role in the global carbon cycle by performing the final steps of organic matter decomposition into methane (CH4 ) and carbon dioxide (CO2 ) in anaerobic environments
Three major pathways of anaerobic archaeal methanogenesis have been described in the literature—acetoclastic, hydrogenotrophic, and methylotrophic methanogenesis [2]
GTDB-Tk classified the genome to the genus level as Methanolobus, in agreement with the original metagenome-assembled genome (MAG) classification by
Summary
Methanogens play a key role in the global carbon cycle by performing the final steps of organic matter decomposition into methane (CH4 ) and carbon dioxide (CO2 ) in anaerobic environments. Methanosarcinaceae is recognized as the most metabolically diverse family, containing genera that can perform all three pathways [4]. Members of the genera Methanolobus and Methanomethylovorans (Methanosarcinaceae) are methylotrophic methanogens, as many experiments on pure cultures have shown growth and methane production with methylotrophic substrates but not acetate or hydrogen/carbon dioxide [5,6,7,8,9,10,11,12,13,14,15]
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