Going Viral

Virginia Edgcomb, Geology & Geophysics


2015 OLI Funded Project


There is increasing evidence for marine oxygen minimum zone (OMZ) expansion and intensification due to increasing stratification, decreasing ventilation and declining gas solubility related to global warming.  OMZ expansion has significant impacts on marine microbial communities that are the engines of biogeochemical cycling in the oceans, and alters production and cycling of trace gases such as methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2).  These gases are important for metabolism and can have a pronounced feedback on climate.  While there are ongoing biogeochemical, metagenomics (gene coding potential) and metatranscriptomic (gene transcripts) investigations of microbiota (Bacteria, Archaea and single-celled Eukarya) and processes along marine redoxclines including OMZs, no such study to date has incorporated consideration of virus activities,their impact on host metabolism and carbon and other nutrient cycling.  There are millions of viruses per ml of seawater and significant fractions of microbial communities are infected at any given time.  Viruses are thought to significantly shape marine ecosystems through lysis of prey and release of dissolved organic matter.  They also are known to carry selected host metabolic genes spanning all of central metabolism and to transfer and express those genes during infection.  This has the potential to significantly impact microbial activities.
The objective of this proposal is to capitalize on samples of opportunity that were collected in 2014 explicitly for potential viral studies from six water layers along the oxycline of the permanently stratified and classic anoxic endmember water column of Cariaco Basin, Venezuela.  There is a long history of time series work on microbial communities in Cariaco Basin, and available historical and contextual environmental data are invaluable for interpretation of viral metagenome data.  The value of these viral samples is greatly increased by availability of whole microbial community (Bacteria, Archaea, and microbial eukayotes) diversity, metagenome (genome coding potential), and metatranscriptome (gene transcripts) data for the same water samples.  Analysis of viral metagenomes from these six samples interpreted in the context of available microbial community and geochemistry data for the same water features will allow unprecedented insights into impacts of double stranded DNA viruses in oxygen-depleted water columns.  As the impact of viruses on redoxcline microbial communities and chemoautotrophic processes is still unknown, a proposal submitted to NSF to do this work would have a low likelihood of success, as it would be deemed too risky.  It is our aim in this OLI project to demonstrate how viral and microbial meta-‘omics’ and biogeochemical data can be integrated to obtain a better understanding of water column processes, and to leverage the results of this investigation of redoxcline viruses to obtain future collaborative funding for a truly whole community (including viruses) investigation of other OMZ water columns of global importance that show seasonal expansion/intensification.