Linking genetic change to community evolution: insights from studies of bacteria and bacteriophage

A major goal of community ecology is to link biological processes at lower scales with community patterns. Microbial communities are especially powerf ul model systems for making these links. In this article, we review recent studies of laboratory communities of bacteria and bacteriophage (viruses th at infect bacteria). We focus on the ecology and evolution of bacteriophage -resistance as a case study demonstrating the relationship between specific genes, individual interactions, population dynamics, community structure, and evolutionary change. In laboratory communities of bacteria and bacterio phage, bacteria rapidly evolve resistance to bacteriophage infection. Diffe rent resistance mutations produce distinct resistance phenotypes, differing , for example, in whether resistance is partial or complete, in the magnitu de of the physiological cost associated with resistance, and in whether the mutation can be countered by a host-range mutation in the bacteriophage. T hese differences determine whether a mutant can invade, the effect its inva sion has on the population dynamics of sensitive bacteria and phage, and th e resulting structure of the community. All of these effects, in turn, gove rn the community's response to environmental change and its subsequent evol ution.