Evidence for quorum sensing and differential metabolite production by Ruegeria pomeroyi in response to DMSP

Microbial alteration and remineralization of organic matter in the ocean play essential roles in the carbon cycle. The impact of individual compounds as either growth substrates or infochemicals is still poorly constrained in models, particularly for organisms with relatively versatile genomes. Here, we use metabolomics techniques to characterize the response of a heterotrophic marine bacterium, Ruegeria pomeroyi DSS-3, to growth on the abundant algal metabolite dimethylsulfoniopropionate (DMSP). DMSP is a valuable source of reduced carbon and sulfur as well as a chemo-attractant. It is present at higher concentrations during phytoplankton blooms. When cultivated on DMSP, R. pomeroyi synthesized a quorum sensing molecule, N-(3-oxotetradecanoyl)-L-homoserine lactone, which was not synthesized at the same levels during growth on propionate, another carbon substrate. More broadly, we observed differential production of intra- and extracellular metabolites with implications for nitrogen assimilation and microbial cross-feeding. This multi-faceted response suggests that R. pomeroyi uses a two-component regulatory system dependent on the presence of DMSP and high cell densities to activate a suite of metabolic changes that may shape how it accesses nutrients and impacts the surrounding microbial consortium.