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Research article - Peer-reviewed, 2022

Growth-stage-related shifts in phytoplankton endometabolome composition set the stage for bacterial heterotrophy

Olofsson, Malin; Ferrer-Gonzalez, Frank X.; Uchimiya, Mario; Schreier, Jeremy E.; Holderman, Nicole R.; Smith, Christa B.; Edison, Arthur S.; Moran, Mary Ann


Phytoplankton-derived metabolites fuel a large fraction of heterotrophic bacterial production in the global ocean, yet methodological challenges have limited our understanding of the organic molecules transferred between these microbial groups. In an experimental bloom study consisting of three heterotrophic marine bacteria growing together with the diatom Thalassiosira pseudonana, we concurrently measured diatom endometabolites (i.e., potential exometabolite supply) by nuclear magnetic resonance (NMR) spectroscopy and bacterial gene expression (i.e., potential exometabolite uptake) by metatranscriptomic sequencing. Twenty-two diatom endometabolites were annotated, with nine increasing in internal concentration in the late stage of the bloom, eight decreasing, and five showing no variation through the bloom progression. Some metabolite changes could be linked to shifts in diatom gene expression, as well as to shifts in bacterial community composition and their expression of substrate uptake and catabolism genes. Yet an overall low match indicated that endometabolome concentration was not a good predictor of exometabolite availability, and that complex physiological and ecological interactions underlie metabolite exchange. Six diatom endometabolites accumulated to higher concentrations in the bacterial co-cultures compared to axenic cultures, suggesting a bacterial influence on rates of synthesis or release of glutamate, arginine, leucine, 2,3-dihydroxypropane-1-sulfonate, glucose, and glycerol-3-phosphate. Better understanding of phytoplankton metabolite production, release, and transfer to assembled bacterial communities is key to untangling this nearly invisible yet pivotal step in ocean carbon cycling.

Published in

ISME Communications
2022, volume: 2, number: 1, article number: 28

Authors' information

Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
University of Georgia
Ferrer-Gonzalez, Frank X.
University System of Georgia
Uchimiya, Mario
University of Georgia
Schreier, Jeremy E.
University System of Georgia
Holderman, Nicole R.
University of Georgia
Smith, Christa B.
University System of Georgia
Edison, Arthur S.
University System of Georgia
Moran, Mary Ann
University of Georgia

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