Bacterial and archaeal profiling of hypersaline microbial mats and endoevaporites, under natural conditions and methanogenic microcosm experiments
Bacterial and archaeal community structure of five microbial communities, developing at different salinities in Baja California Sur, Mexico, were characterized by 16S rRNA sequencing. The response of the microbial community to artificial changes in salinity–sulfate concentrations and to addition of trimethylamine was also evaluated in microcosm experiments. Ordination analyses of the microbial community structure showed that microbial composition was distinctive for each hypersaline site. Members of bacteria were dominated by Bacteroidetes and Proteobacteria phyla, while Halobacteria of the Euryarchaeota phylum was the most represented class of archaea for all the environmental samples. At a higher phylogenetic resolution, methanogenic communities were dominated by members of the Methanosarcinales, Methanobacteriales and Methanococcales orders. Incubation experiments showed that putative hydrogenotrophic methanogens of the Methanomicrobiales increased in abundance only under lowest salinity and sulfate concentrations. Trimethylamine addition effectively increased the abundance of methylotrophic members from the Methanosarcinales, but also increased the relative abundance of the Thermoplasmata class, suggesting the potential capability of these microorganisms to use trimethylamine in hypersaline environments. These results contribute to the knowledge of microbial diversity in hypersaline environments from Baja California Sur, Mexico, and expand upon the available information for uncultured methanogenic archaea in these ecosystems.
KeywordsHypersaline microbial mats Microbial diversity Methanogenesis Microcosm incubations 454 pyrosequencing
This project was supported by CONACYT grant 105969-Z (2008–2014) to ALC and by grants to BMB by NASA’s Exobiology program. We are grateful with Exportadora de Sal, S.A. for access to the Guerrero Negro field site. We thank to Adrian Mungia for technical assistance in the library prep and 454 pyrosequencing. We thank ‘Unidad de Secuenciación Masiva y Bioinformática’ at the ‘Laboratorio Nacional de Apoyo Tecnológico a las Ciencias Genómicas’, CONACyT #260481, Instituto de Biotecnología/UNAM for computational resources used for the bioinformatics analyses. We are thankful to Santiago Cadena Rodríguez for lab assistance and for his contributions on the interpretations of the results. We are very appreciative of many helpful discussions with Cheryl Kelley and for the field assistance of Angela M. Detweiler.
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