Bacterial transcriptional response to labile exometabolites from photosynthetic picoeukaryote Micromonas commoda

Frank X. Ferrer-González, Maria Hamilton, Christa B. Smith, Jeremy E. Schreier, Malin Olofsson & Mary Ann Moran

ISME Communications

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Much of the growth of heterotrophic marine bacteria is dependent on the dissolved organic carbon released by phytoplankton, yet the composition of algal exudates and how this may differ among taxa is still poorly understood. Here, we have utilized transcriptomic data from co-cultures of model marine bacteria grown with the picoeukaryote alga, Micromonas commoda, to characterize the exometabolite pool of this phytoplankton. We predicted that the bacteria recognized 38 different metabolites released by M. commoda, based on the expression of catabolic and transporter genes. Several of these metabolites, including some sulfur- and nitrogen- containing compounds, were unique to this alga, when compared to the exometabolites released by the diatom Thalassiosira pseudonana, as assessed previously using the same method. These results suggest that as phytoplankton communities shift towards dominance by smaller picophytoplankton over larger diatoms in a warming ocean, the pool of substrates available to heterotrophic bacteria may also be altered, with implications for global biogeochemical cycles.