Evolution and intracellular cooperation in an ancient nutritional symbiosis

• Applicant: Professor Dr. Harald Gruber-Vodicka
• Subject Area: Evolution, Anthropology ; Animal Physiology and Biochemistry ; Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 495424895

Intracellular symbiosis is a key source for evolutionary innovation and e.g. allows animal hosts to directly rely on chemosynthesis for nutrition. This project focuses on the evolution and function of one of the most deeply integrated animal-bacterial intracellular symbioses in metazoans - mouthless Paracatenula flatworms and their chemosynthetic Riegeria symbionts. Compared to the highly reduced nutritional symbionts in insects, Riegeria encodes a much more versatile metabolism that can generate all building blocks of life. In the first part of this project, we will test, how the evolutionary dynamics are affected by this large and essential core genome by comparatively analyzing metagenomic datasets of 38 globally sampled host species. The second part of the project will unravel the mechanisms of cellular metabolic integration. The Riegeria symbionts produce PHA bioplastics for storage that animals cannot use. Surprisingly, the symbionts possess no PHA depolymerase, but instead the hosts expresses several variants of this essential enzyme for PHA use. We will analyze the function and the expression patterns in the host and will explore a possible transfer of such enzymes to the symbiont, testing for organelle-level intracellular integration.

• DFG Programme: Research Grants