Osmolyte synthesis and utilization in the marine bacterium Vibrio natriegens

Marine microorganisms maintain cellular osmotic balance with osmolytes that they synthesize or obtain from their environment. Many osmolytes are small, organic molecules, including sugars, amino acids, methylamines, and methylsulfonium compounds, and can be present at millimolar concentrations inside of microbial cells. These molecules contribute to the labile dissolved organic carbon pool and are exchanged through the microbial food web. Vibrio natriegens is a heterotrophic marine bacterium that primarily utilizes ectoine as an osmolyte when grown with glucose as its sole carbon substrate. However, it has the capability to synthesize the osmolyte glycine betaine, which has been identified as a prevalent osmolyte found on marine sinking particles. To explore osmolyte utilization and production in V. natriegens we use liquid chromatography- tandem mass spectrometry (LC-MS/MS)-based targeted metabolomics. We have identified how abundances of osmolytes and other metabolites respond to changes in salinity and temperature. To further characterize how substrates provided by other microbial community members influence production of osmolytes we grew V. natriegens with precursor substrates such as phosphatidylcholine and choline to determine how osmolyte production shifted. These results provide insight into the dynamics of production and utilization of microbial metabolites that are important currency in marine microbial food webs.