How to avoid competition: experimental evolution of dispersal and social behavior in microbes

Description:

Whereas motile organisms such as most animals can avoid local competition for resources via migration, non-motile organisms such as plants have limited abilities to do so (e.g. by producing seeds).  Non-motile organisms may partially compensate for local competition by evolving social traits that increase the reproductive output of the group, which may be selected because of high local relatedness. Theoretical studies indicate that an intermediate degree of dispersal is optimal for such social behavior to evolve (West et al. 2002).   We want to study the evolution of competition avoidance in non-motile bacteria and fungi using laboratory evolution experiments.  For instance, we have strains of the non-motile bacterium Escherichia coli that have evolved either with or without mixing for 900 generations on agar surface (Habets et al. 2006, 2007).  We are interested to study whether evolution without mixing has led to increased dispersal behavior (e.g. by producing surfactants that allow them to spread across the surface) or, alternatively, to increased social behavior resulting in higher yield rather than growth rate.  One way to study these changes is to compare colony morphologies, competitive fitness and yield of evolved clones from mixed relative to non-mixed environments.  But also new evolution experiments can be done with a surfactant-producing strain of the bacterium Pseudomonas fluorescens (collaboration with Jos Raaijmakers, Phytopathology) and with the fungi Aspergillus and Termitomyces to study the evolvability of dispersal behavior in short-term evolution experiments.  One possibility in these experiments is to introduce predators, such as Caenorhabditis elegans for E. coli or mites for fungi, as potential vectors for dispersal.

Used skills:

Basic microbiological techniques and molecular methods to monitor the results of the evolution experiments. Theoretical modeling. Statistical analysis.

Requirements:

Molecular and Evolutionary Ecology (GEN20304) and Genetic Analyses Tools and Concepts (GEN30306) provide a good preparation.

Contact

Arjan de Visser (arjan.devisser@wur.nl), Duur Aanen (duur.aanen@wur.nl) or Fons Debets (fons.debets@wur.nl)

Reference:

Habets et al. 2006. The effect of population structure on the adaptive radiation of microbial populations evolving in spatially structured environments. Ecol. Lett. 9: 1041-1048;  Habets et al. 2007. Spatial structure inhibits the rate of invasion of beneficial mutations in asexual populations. Proc. R. Soc. London B 274: 2139-2143; West et al. 2002. Cooperation and conflict between relatives. Science 296: 72-75.