Effects of predation on microbial communities

In all terrestrial, limnic, and marine environments bacteria constantly face predation. Bacterivorous predators include besides other bacteria like Bdellovibrio or Myxococcus, also protists such as various ciliates, flagellates, or amoebae. Grazing by protists directly shapes the structure and dynamics of bacterial communities. Moreover, it is considered a major selective force in promoting bacterial adaptions, thus accelerating bacterial evolution. Antipredator adaptations are classified as pre-ingestional, when bacteria evolve larger sizes, a faster swimming speed, or the ability to form aggregates, thus decreasing the risk of being engulfed. In contrast, post-ingestional adaptations are cases, in which bacteria evolved to evade digestion.

We use a range of protists with distinct feeding modes (e.g. the particle feeder Tetrahymena thermophila or the surface feeder Acanthamoeba polyphaga) in combination with different bacterial prey species to investigate whether metabolic cross-feeding and/or the formation of multicellular clusters helps bacteria to resist predation. A second line of research is the attempt to establish endosymbiotic associations between protists and their prey. Here we are particularly interested in the causal factors as well as the evolutionary consequences. Together, we use the interaction between bacteria and protists as a model system to address fundamental ecological and evolutionary questions relating to the evolution of endosymbiosis, multicellularity, or predator-prey coevolution.

Researchers:

Silvia Kost, Linea Mushal, Christian Kost