Bacteria associated with marine and estuary sediments mediate redox cycling of iron and sulfur. However, the vast majority of the microorganisms there are uncultured, thus we little is known about how these biogeochemical processes are partitioned in these communities. We employed high-throughput random DNA sequencing from different redox regimes from White Oak River (North Carolina) estuary sediments. We were able to reconstruct 82 near-complete genomes belonging to a variety of novel and uncultured bacteria. We identified numerous genes involved in iron (eg. mtrABC) and sulfur oxidation (sox and rdsr) and reduction pathways in these genomes. Among the most abundant organisms in the sulfate-rich layer (8-12 cm depth) are a newly identified lineage of Gammaproteobacteria that have the potential for anaerobic sulfur oxidation coupled to nitrate and nitrite reduction. Iron oxidation appears to be driven by Betaproteobacteria (related to Sideroxydans lithotrophicus) and localized to the upper sulfate-rich zone as well. Interestingly, some of the Gammaproteobacteria capable of sulfur oxidation also have the genetic potential for anaerobic Fe(III) oxide reduction with acetate or lactate as electron donors. These uncultured Gammaproteobacteria have several unique c-type and multi-heme cytochromes implicated in electron transfer for iron reduction. This genomic reconstruction begins to resolve which bacteria are driving iron and sulfur cycling in the WOR sediments, and identifies potential geochemical processes that can be verified by targeted process measurements and geochemical gradient studies in estuarine environments.

Harnessing community genomics to understand microbial iron and sulfur cycling in estuary sediments

249th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.