Abstract

We are investigating the deep biosphere of the subseafloor basaltic crust on the eastern flank of the Juan de Fuca Ridge by accessing pristine crustal fluids via Circulation Obviation Retrofit Kit (CORK) sampling and instrumentation platforms. Second-generation CORKs installed within Integrated Ocean Drilling Program boreholes provide unprecedented opportunities to study the microbial ecology and biogeochemistry of fluids circulating in the sediment-covered oceanic basement. In the summers of 2008-2011, a unique large-volume sampling system was used to collect some of the only large volume pristine basement fluid samples available for microbiological studies to date, from a 3.5 Myr-old basalt-hosted basement aquifer that is covered by 260m of sediment. On an annual scale, the microbial community appears to be temporally dynamic; however, some common community members are shared between sample years. We will obtain nucleic acid sequence data from the metagenome of two deep subsurface microbial community samples (one each from field seasons 2010 and 2011) and the metatranscriptome of one corresponding sample, as well as amplify the genomes of a subset of single cells. Due to the well-known difficulties in obtaining pristine sub-seafloor ocean crustal fluids, these samples offer an unmatched opportunity to investigate the community genomics of cells inhabiting the deep subseafloor biosphere.