DARC Microbes

: This project investigates the genetic potential and activity of uncultured microorganisms in the meso- and bathypelagic oceanographic layers (200 to 4,000 m water depth) to characterize deep-sea microbiology and address a discrepancy in the marine carbon cycle. Using high-pressure sampling and incubation vessels, metagenomics, metatranscriptomics, and stable-isotope experiments coupled to single-cell isotope analyses via nanoSIMS, we will (1) quantify microbial anabolic activity in general and chemoautotrophy, mixotrophy, and heterotrophy specifically at bulk and single-cell levels, (2) characterize the diversity and distribution of genes and transcripts involved in chemoautotrophy and heterotrophy, (3) identify novel chemoautotrophs and mixotrophs and quantify their contribution to carbon cycling, and (4) investigate the ability of a major chemoautotrophic deep-sea lineage, the Marine Group I Thaumarchaeota, to utilize organic matter. The overarching hypothesis is that (1) deep-sea microorganisms are more active than currently appreciated, (2) that the organic carbon required to support this activity is provided – at least in part – by higher rates of endogenous inorganic carbon fixation, and (3) that this fixation is performed by more phylogenetically and metabolically diverse chemoautotrophs/mixotrophs than currently known. This work has the potential to reveal novel functions in uncultured microbes and change our understanding of marine carbon cycling. Data will be available through BCO-DMO (Project #868163).