Something New from Something Old?
Identifying Factors that Constrain Life 2500 Meters below the Surface
Kelly Wrighton, Ohio State University
The terrestrial subsurface, a rock-hosted environment far removed from the sun’s penetrating rays, remains one of the least studied microbial habitats on earth. In this talk, I take advantage of recent drillings into 400 million-year-old shales to examine features that enable life to colonize these habitats. Our study shows that only a handful of surface microorganisms, when injected via drilling fluids nearly a mile below, can survive incredible conditions. These microorganisms live amid a rock matrix, growing under elevated temperatures, pressures 600 times greater than the surface, and salinities four times that of the ocean. Recent advances in microbial genomics now make it possible to assemble a DNA-based metabolic blue print of these organisms, gaining insight into the features that allow survival. Factors shared amongst the organisms include adaptations to brine-level salinities and the ability to withstand or even degrade biocides. Findings from our lab and others suggest these microbial communities form an interconnected metabolic network that degrade methyl-containing osmoprotectants and biocides to yield biogenic methane. Moreover, all microorganisms existing in shales after nearly a year have an active viral defense system, and many can be linked to viral partners, suggesting the ability to ward off viral predation is another feature of these new subsurface inhabitants. Collectively this study highlights the resilience of microbial life to adapt to and colonize a new habitat structured by physical and chemical features far different than their origin.