Methanogens at the top of the world: occurrence and potential activity of methanogens in newly deglaciated soils in high-altitude cold deserts in the Western Himalayas

Abstract

Methanogens typically occur in reduced anoxic environments. However, in recent studies it has been shown that many aerated upland soils, including desert soils also host active methanogens. Here we show that soil samples from high-altitude cold deserts in the western Himalayas (Ladakh, India) produce CH4 after incubation as slurry under anoxic conditions at rates comparable to those of hot desert soils. Samples of matured soil from three different vegetation belts (arid, steppe, and subnival) were compared with younger soils originating from frontal and lateral moraines of receding glaciers. While methanogenic rates were higher in the samples from matured soils, CH4 was also produced in the samples from the recently deglaciated moraines. In both young and matured soils, those covered by a biological soil crust (biocrust) were more active than their bare counterparts. Isotopic analysis showed that in both cases CH4 was initially produced from H2/CO2 but later mostly from acetate. Analysis of the archaeal community in the in situ soil samples revealed a clear dominance of sequences related to Thaumarchaeota, while the methanogenic community comprised only a minor fraction of the archaeal community. Similar to other aerated soils, the methanogenic community was comprised almost solely of the genera Methanosarcina and Methanocella, and possibly also Methanobacterium in some cases. Nevertheless, ~103 gdw−1 soil methanogens were already present in the young moraine soil together with cyanobacteria. Our results demonstrate that Methanosarcina and Methanocella not only tolerate atmospheric oxygen but are also able to survive in these harsh cold environments. Their occurrence in newly deglaciated soils shows that they are early colonizers of desert soils, similar to cyanobacteria, and may play a role in the development of desert biocrusts.

Comparative genomics of three Methanocellales strains reveal novel taxonomic and metabolic features

“…Methanocellales appears to have exceptional aero‐tolerant abilities, and all three strains encode a substantial number of genes involved in antioxidant resistance (Erkel et al ., ; Angel et al ., 2011; 2012; Sakai et al ., ; Yuan et al ., ; Lü and Lu, ; Aschenbach et al ., ). However, a robust antioxidant system would also need a strong energy source that is oxygen tolerant, as many reactions consume reducing equivalents (Imlay, ).…”

“…For example, Methanocellales and Class II methanogens are commonly found to be active in rice soil and wetland where low H 2 concentrations of 1–10 pa prevail (Conrad et al ., ; Liu and Whitman, ; Thauer et al ., ). Methanocellales also shares some unique habitats with Class III methanogens, such as upland soils where aeration and desiccation are common, although methanogens typically occur in reduced anoxic and moisturized environments (Angel et al ., 2011; 2012; Aschenbach et al ., ). Genome sequences for M. arvoryzae , M. paludicola and M. conradii have begun to elucidate basic features of the Methanocellales ' lifestyle, which include hydrogenotrophic methanogenesis and aerotolerance (Erkel et al ., ; Sakai et al ., ; Lü and Lu, ).…”

Crop rotation of flooded rice with upland maize impacts the resident and active methanogenic microbial community

“…and Methanocella spp. are conspicuous residents of dry and aerated soils, even in desert biological soil crusts (Nicol et al ., ; Poplawski et al ., ; Angel et al ., ; Conrad et al ., ; Aschenbach et al ., ).…”

Microbial trophic interactions and mcrA gene expression in monitoring of anaerobic digesters

“…However, it has been demonstrated that these microorganisms are also able to grow in aerated places like deserts soils (Aśchenbach et al, 2013). Annually, approximately 600 million metric tons of methane is produced.…”