Thalassiosira pseudonana CCMP1335 endometabolite uptake by Ruegeria pomeroyi DSS-3

The ocean’s temperature increase has fundamental implications for physiological rates and processes of marine microbes. In this study, a marine diatom Thalassiosira pseudonana CCMP1335 was acclimated for three months at temperatures below (14°C), equal to (20°C), and above (28°C). Heterotrophic bacterium Ruegeria pomeroyi DSS-3 was inoculated into cultures, and transporter expression was compared between temperatures. R. pomeroyi transporter expression leveraged as a biosensor of available diatom exometabolites indicated temperature-related substitution of diatom osmolytes dimethylsulfoniopropionate (DMSP), dihydroxypropanesulfonate (DHPS), and homarine (dominating carbon transfer at lower temperatures) with glycine betaine and choline (dominating at higher temperatures). T. pseudonana endometabolome pools and biosynthetic pathway expression indicated increased availability of amino acids and glycerol-3-phosphate at higher temperatures. Overall trends across datasets supported a greater importance of organic sulfur compounds in diatom-bacterial metabolite transfer at lower temperatures and greater importance of organic nitrogen compounds at higher temperatures.