PARENT SESSION
Contributed Oral Session 59: Bacterial Communities and Diversity
Tuesday, August 9, 1:30 PM - 5:00 PM, Meeting Room 515 A, Level 5, Palais des congrès de Montréal
Coevolutionary dynamics of host-parasitoid interactions: Phage attacks and bacteria fights back.
Weitz, Joshua*,1, Hartman, Hyman2, Levin, Simon1, 1 Department of Ecology and Evolutionary Biology, Princeton, NJ, USA2 Department of Biology, Cambridge, MA, USA
ABSTRACT- The long-term dynamics and composition of microbial communities in natural environments reflect, in part, coevolutionary interactions of bacteria and bacteriophage. Bacteriophage enter host cells via membrane-bound surface receptors that are often responsible for nutrient uptake. As such, a selective pressure will exist for the bacteria to modify its receptor configuration and, in turn, for the phage to modify its tail fiber. A mathematical model describing generalized trait adaptations in host-parasitoid systems is developed using the framework of adaptive dynamics and applied to bacteria-bacteriophage systems. Bacteria host strains differ in their efficiency of resource uptake and phage strains differ in their host-preference for adsorption, extending earlier efforts to describe bacteria-bacteriophage interactions as that of an exclusive lock and key. We solve the mathematical model that encompasses short (ecological) and long (evolutionary) time scales, finding the conditions and governing dimensionless parameters necessary for coevolutionary diversification. We confirm these analytical calculations via stochastic Monte Carlo simulations of populations evolving under typical chemostat conditions with fixed washout rate and inflow resource density. We find that multiple quasispecies of bacteria and phage can co-exist in a homogeneous medium with a single resource. When such a diversification occurs, quasispecies of phage are able to adsorb effectively to only a limited subset of the total number of quasispecies of bacteria, i.e. functional differences emerge directly as a consequence of repeated invasions of mutant strains. Finally, we discuss means to extend these results to interactions which include a latent phase, as well as address the relevance of the model to studies of bacteria and bacteriophage in the chemostat.
Key words: Evolutionary ecology, Adaptive dynamics, Bacteriophage, Receptor