Experimental coevolution between C. elegans and its microparasite B.thuringiensis: phenotypic consequences and its molecular genetic basis

Host-parasite interactions are believed to result in rapid evolutionary change due to the strong selection pressures involved and the need for each antagonist to continually adapt to the other. While theoretical predictions of the dynamics of host-parasite coevolution have been available for some time, empirical evidence is still limited. We study host-parasite coevolution using the nematode Caenorhabditis elegans and the bacterial pathogen Bacillus thuringiensis. Due to the short generation time of C. elegans (approximately 3-4 days), it is possible to perform experimental evolution, where host and parasite coevolve together in the laboratory, in such a way that we expect the consequences of coevolution to be detectable for both host and parasite. Using this system we previously demonstrated that coevolution leads to multiple reciprocal changes in both antagonists, including changes in the traits of direct relevance to the interaction (parasite virulence, host resistance), strong indications of reciprocal life history trade-offs, increased rates of genetic change, and elevated genetic diversity (see our publication list). In our current experiments, we are assessing the difference between coevolution and one-sided adaptation (only one antagonist is allowed to evolve and adapt, while the other is always added from a stock culture), and also the importance of effective population size for the dynamics of coevolution. Moreover, we are also analysing the genomic consequences of coevolution using next generation sequencing of ancestral and evolved populations, which will provide important information about the genetic basis of evolution. Therefore, experimental coevolution of C. elegans and B. thuringiensis, combined with genetic and phenotypic analyses, will allow us to test predictions of host-parasite coevolutionary theory.

Involved people: Leila El Masri, Andrei Papkou, Mike-C. Barg, Manja Saebelfeld, Rebecca Schalkowski, Anna Sheppard, Hinrich Schulenburg

Collaborators: Philip Rosenstiel, Matthias Barann (ICMB, Kiel), Henrique Teotonio (Lisboa, Portugal), Christina Nielsen-LeRoux, Michel Gohar, Vincent Sanchis (all Guyancourt, France), Heiko Liesegang, Elzbieta Brzuszkiewicz, Rolf Daniel (Göttingen, Germany), Joachim Kurtz (Münster, Germany), Erich Bornberg-Bauer, Antoine Branca, Sarah Behrens (Münster, Germany), Rebecca Schulte (Osnabrück, Germany), Sylvia Cremer (Vienna, Austria)

German Science Foundation Priority Programme SPP 1399 on host-parasite coevolution; projects SCHU 1415/8-1 and 9-1