Organic Osmolyte Cycling

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Marine phytoplankton make up only ~1-2% of global plant carbon, yet they are responsible for approximately 40% of global carbon fixation. About 50% of this fixed organic carbon is then consumed by heterotrophic bacteria each day, representing a large flux of energy and matter. A portion of this flux is organic osmolytes, which are small molecules that are either synthesized or transported into cells to maintain osmotic balance across cell membranes. In high salinity environments, like the ocean, microorganisms maintain high concentrations of these molecules in the cytosol due to the high ionic strength of their environment. Since these are small molecules that can be transported across cell membranes without extracellular processing, osmolytes are important carbon substrates for heterotrophs in these environments. In our lab we work to develop methods to better measure these molecules with mass spectrometry, study their rates of production and uptake, and characterize the environmental factors that determine the abundances of these molecules in the ocean, salt marshes, and estuaries.