Nearly every major bacterial lineage studied to date possesses strains that produce protein-based toxins that are thought to function as anti-competitor compounds. Toxin production occurs stochastically and often involves lysis of the producing cell. Such lysis can be seen as a form of indirect altruism because while the producer dies, its latent clones are immune to the released toxin and benefit from having other susceptible competitors killed. As with other forms of altruism, free riders exist in this system as well—cells that are resistant to the toxin, but do not produce it. In this talk, I will explore variousaspects of the ecology and evolution of these toxin-producing communities. I will start with a general model to investigate conditions where altruism (or spite) can be maintained. We will then move to a specific case involving the ecoevolutionary dynamics of a community of toxin-producing Escherichia coli. I will review some older work on non-transitive (rock-paper-scissors) coexistence and discuss the evolution of competitive restraint (another form of altruism). I will then turn to some current work on the origins of novel toxins using a directed evolution approach. This pursuit of origins has led to a new evolutionary hypothesis, as well as some unusual perspectives on the molecular underpinnings of this system.
Ben Kerr received his PhD in biological sciences from Stanford University in 2002. While at Stanford, he worked with Marcus Feldman on modeling the evolution of flammability in resprouting plants, the evolution of animal learning, and the evolution of altruism. He also worked with Brendan Bohannan on experimental evolution within microbial systems and with Peter Godfrey-Smith on some philosophical issues arising in the levels of selection controversy. Kerr then spent 3 years as a postdoctoral research associate at the University of Minnesota, where he worked with David Stephens on modeling impulsive behavior in blue jays, with Tony Dean on the evolution of cooperation within a microbial host-pathogen system, and with Claudia Neuhauser on spatial dynamics within model population genetic systems. Kerr joined the faculty of the University of Washington in 2005. His lab currently uses a combination of mathematical analysis, computer simulation, and laboratory experiments with microbes to explore theoretical and empirical perspectives on topics in ecology, evolutionary biology, and the philosophy of biology.
This seminar is presented by the Research School of Biology and the Centre for Philosophy of the Sciences. All welcome, no registration required.