No abstract

The Salton Sea Trough has a range of geothermal features, including mud volcanoes, pots, and seeps that express fluids at temperatures ranging from ambient to 65 to 100 C. The features produce 99% CO2/0.5% CH4 gas of a thermogenic origin and contain hydrothermally-produced petroleum. The mud/clay from the Davis-Schrimpf mud volcanoes has an elemental sulfur (S0) concentration of 317 microM, suggesting that sulfur metabolism should be important in the system. Surprisingly, there has been very little microbiological characterization of these features. Described here are microbial communities, determined by Illumina sequencing of the 515F – 806R 16S rRNA gene fragment, from mud volcanoes/seeps from the Davis-Schrimph seep field and nearby areas with surface feature temperatures from ambient, 65 C, and 100 C. In addition, we have characterized the communities that developed over 1 month at 65 C in enrichment cultures from the 65 C mud volcanoes incubated with a range of electron acceptors (ferrihydrite, S0, SO42-, and S2O32-) and electron donors (tryptone/yeast/casamino acids, crude oil, and CH3CO2-). The 65 C mud and enrichment culture communities were generally predominated by autotrophic H2-oxidizers and organotrophic H2-producers, acetogens, acetotrophs and heterotrophic S0, SO42-, and S2O32- reducers, including many relatives of microbes previously observed in the deep subsurface and from petroleum fields or production waters. While methanogens were present, they were generally at low levels, and few obvious methylotrophs or anaerobic methane oxidizers were detected. Overall, these results provide evidence for a subsurface lithoautotrophic microbial ecosystem (or SliME) in the Salton Sea trough subsurface.