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What Silverware to Use When You're 100,000 Years Late for Dinner

Andrew Steen, University of Tennessee - Knoxville

21 April 2017

Subsurface marine sediments contain active microbial communities. These communities live mysterious lifestyles, but what we do know is that they're weird: cell carbon turnover times (something like a microbial 'lifetime') are on the order of hundreds to tens of thousands of years, and many organisms are only distantly related to organisms that have been grown in culture. Many of these organisms appear to be heterotrophs which gain carbon and energy from consuming recalcitrant organic carbon - very, very slowly. In this talk, Dr. Steen will address how this is possible. One important pathway appears to be the production of extracellular enzymes. Much like the digestive enzymes that humans produce in the gut to break down food, these enzymes break down complex macromolecules outside of the cell into fragments that are small enough to be transported across cell membranes. The nature and activity of these enzymes can yield some insight into the type of organic carbon that subsurface microorganisms are seeking. Dr. Steen will also address some more speculative abiotic/biotic coupled pathways by which recalcitrant organic carbon can be made bioavailable to heterotrophic microorganisms in subsurface sediments.