S41: Linking metagenomes to metabolite profiles of deep-sea sediment cores from the Gulf of Mexico following the Deepwater Horizon oil spill

Marine subsurface environments, such as deep-sea sediments, house abundant and diverse microbial communities that are believed to influence large-scale geochemical processes including the biotransformation of numerous crude oil constituents.  Following the Deepwater Horizon (DWH) oil spill, microbial communities in the Gulf of Mexico are proposed to be responsible for the intrinsic bioremediation of crude oil.  While hydrocarbon contamination has been shown to enrich for aerobic, oil-degrading bacteria in deep-seawater habitats, relatively little is known about deep-sea sediment communities where low oxygen levels may hinder such a response.  We used metagenomic analysis coupled to metabolite profiling of deep-sea sediment samples from the Gulf of Mexico to elucidate potential pathways for the microbial metabolism of hydrocarbons.  The presence of aerobic microbial communities and associated functional genes was consistent among all samples, whereas, a greater number of Deltaproteobacteria and anaerobic functional genes were found in sediments closest to the DWH blowout site.  Metabolite profiling also revealed a greater number of putative metabolites in sediments surrounding the blowout zone relative to a background site located 127 km away.  The mass spectral analysis of the putative metabolites revealed that alkylsuccinates remained below detection levels, but a homologous series of benzylsuccinates (with carbon chain lengths from 5 to 10) could be detected.  Our findings suggest that increased hydrocarbon exposure enriches for Deltaproteobacteria known to be capable of anaerobic hydrocarbon metabolism and provides evidence of an active microbial community metabolizing aromatic hydrocarbons in deep-sea sediments of the Gulf of Mexico.