Intracellular metabolites from an experimental manipulation of marine microorganisms

The marine environment holds one of the largest pools of reduced organic carbon on Earth. Within this organic carbon are metabolites produced as a result of microbial activity. This project considers the effects of predation and viral lysis on the metabolites found in the surface ocean. Using seawater from the surface ocean, we experimentally manipulated levels of predation and viral lysis. At the beginning and end of the experiment, we sampled the intracellular and extracellular metabolites. The extracts were analyzed using liquid chromatography-based targeted and untargeted metabolomics methods that we have modified for use with marine samples. The untargeted metabolomics data revealed a complex mixture of organic compounds in all of the experimental treatments. However, changes in the majority of the features could not be linked to viral lysis or predation. Within the targeted metabolomics data, increased intracellular levels of osmolytes (glycine betaine, dimethylsulfoniopropionate, proline, and ectoine) were observed under conditions with limited grazing or viral lysis. The molecular insights derived here will explicitly inform our understanding of microbial processes in the surface ocean and the subsequent impacts on the global carbon cycle.