Methanogenic and sulfate reducing activities in a hypersaline microbial mat and associated microbial diversity

Methanogenesis and sulfate reduction are important microbial processes in anoxic hypersaline environments.We evaluated competitive and noncompetitive substrates for stimulation of both processes through incubated microcosms of a hypersaline microbial mat from Guerrero Negro, Baja California Sur, Mexico, and characterized the microbial community composition when added substrates were consumed in microcosms, based on 16S rRNA gene analysis. We report evidence that trimethylamine and methanol stimulate both methanogenic and sulfate reduction activities, being methane production the predominant process. Furthermore, incubations supplemented with acetate and lactate, performed in absence of sulfate, alsoproduced methane apparently driven by hydrogenotrophic methanogenesis. Moreover, 16S rRNA gene amplification showed remarkable differences in the microbial community composition among experimental treatments supplemented with different substrates, displaying Proteobacteria, Hydrogenedentes, Bacteroidetes and Planctomycetes the most abundant bacterial Phyla in all treatments. Archaeal community composition was related to methanogens of the Families Methanosarcinaceae and Methanomicrobiaceae andto the unclassified Marine Benthic Group D, Woesearchaeota and Bathyarchaeota. This information is required to better understand competition between methanogenesis and sulfate reduction, which plays an important role on determining methane fluxes in hypersaline environments.