Project 7

Give and take – substrate shuttling in microbial communities on macroalgae

Prof. Dr. Georg Pohnert (main supervisor)
Institute for Anorganic und Analytic Chemistry, Friedrich Schiller University Jena, Max Planck Institute for Chemical Ecology
Prof. Dr. Martin Kaltenpoth (co-supervisor)
Department of Insect Symbiosis, Max Planck Institute for Chemical Ecology

Diatoms are photosynthetic microalgae that contribute to approximately 20% of global CO2 fixation. These algae were for a long time considered as phototrophs using exclusively photosynthesis to serve their metabolic requirements. We have recently shown that this is not true and that diatoms are surprisingly efficient in taking up dissolved organic matter from the seawater. In their natural environment of the plankton, diatoms are exposed to a plethora of metabolites, especially when competitors and bacteria are present. These metabolites can be assimilated and are incorporated into the metabolome. One of the most dominant phytoplankton groups is thus competing with other heterotrophs for organic material, suggesting that a form of absorbotrophy may have a substantial impact on organic material fluxes in the oceans. This calls for the refinement of our understanding of competition in the marine environment, which is the objective of this project.

Project description:
Within this project, we will address the hypothesis that marine diatoms are interacting with their environment via metabolite exchange. The algae serve both as sources and sinks for organic material dissolved in the ocean waters. We will use a combination of (co-)culturing and metabolomic investigations to follow the metabolic flux during alga-alga interactions. Therefore, we will use macroalgae that serve as a substrate for the settlement of microalgae. To investigate the metabolic flux between these partners one will be labeled with stable non-radioactive isotopes. Using mass spectrometry techniques, we will reconstruct the release and uptake of metabolites during the interaction situation. The developed methodology will also be used to address metabolic fluxes in other systems, like insect symbiosis or microbial communities.
Taken together this project can re-define the role of one of the most proliferative organismic classes in the oceans, the diatoms, within their community.

Candidate profile:
The ideal candidate has a strong interest in analytical investigations, involving mainly top-level mass spectrometry, and is curious to answer questions of ecological impact.


  1. Meyer, N., Rydzyk, A., Pohnert, P. (2022). Pronounced Uptake and Metabolism of Organic Substrates by Diatoms Revealed by Pulse-Labeling Metabolomics. Frontiers in Marine Science.
  2. Vallet, M.; Baumeister, T. U. H.; Kaftan, F.; Grabe, V.; Buaya, A.; Thines, M.; Svatoš, A.; Pohnert, G. (2019). The oomycete Lagenisma coscinodisci hijacks host alkaloid synthesis during infection of a marine diatom. Nature Communications 10, 4938.


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