Proteomic stress response by a novel methanogen enriched from the Great Salt Lake

Methanogenic archaea affect the climate through their production of the greenhouse gas, methane. However, it is unclear how a changing climate and other anthropogenic influences impact methanogen physiology and consequent methane flux. The Great Salt Lake (GSL) is an environment that has been heavily impacted by human activity, more than doubling its salt concentration since the last methanogen was cultured from it in 1985. In this study, we enriched a novel methanogen, for which we propose the name Candidatus Methanohalophilus hillemani, from the GSL at a time when its salinity reached a historical high. Interestingly, Ca. M. hillemani does not increase the expression of energy-conservation or osmotolerance proteins when challenged with salinity or oxygen. In contrast, Ca. M. hillemani prioritizes trace metal uptake and immune functions in response to the presence of the sulfate-reducing bacterium Desulfovermiculus. 16S rRNA gene amplicon data from GSL shore soils with extremely high and variable methane flux indicated the presence of Ca. M. hillemani. Our results show that Ca. M. hillemani is active when challenged with environmental stressors and contributes to the methane flux emanating from the GSL.IMPORTANCEMethanogens are microbes that affect the climate through their production of the greenhouse gas, methane. Changes in climate and land-use patterns are drying up saline lakes, damaging their unique economic and ecological value. As lake levels across the globe fall, it is unclear how methanogens and the amount of methane they produce will concurrently shift. In this study, we measured high methane output from the Great Salt Lake (GSL) across seasons and identified a novel methanogen as part of a larger methanogenic community that is responsible for these emissions. We cultured this novel methanogen from GSL sediments and determined that its methane production was largely unaffected by stress conditions. Our findings indicate that methanogens in saline environments, including a novel cultivated species, may be important and continued sources of methane as salinity increases.