Marine viruses are extremely abundant and diverse. Studies suggest these viruses are important in regulating microbial abundance and diversity and thus may influence nutrient cycling in marine ecosystems. Despite their ecological importance, little is known about the population biology of marine viruses or how these viruses interact with their hosts. This project is examining the coevolution of bacteria and their viruses (phage) in diverse communities and the effect phage/bacteria interactions have on overall bacterial mortality rates. The research is employing a two-pronged approach that will bridge laboratory microcosms with natural communities of marine cyanobacteria and cyanophage. First, natural isolates of cyanobacteria (Synechococcus spp.) and cyanophages are being used to examine whether Synechococcus and cyanophage undergo coevolution, whether phosphate availability changes the outcome of these interactions, and the consequences of these interactions on host mortality. Second, the hypotheses generated in laboratory experiments are being tested in natural marine communities. Synechococcus and cyanophage strains are being isolated from Rhode Island coastal waters over the course of two years. This time series are being used to detect if coevolution is occurring and how it affects the genotypic and phenotypic diversity of cyanobacteria and cyanophages in the natural environment. This project is the first to test whether cyanobacteria and cyanophage undergo coevolution and whether coevolution is likely to occur on a time scale important to their population dynamics. Furthermore, the experiments are examining the consequences of viruses on marine host populations from a population biology perspective, whereas previous studies have examined only aggregate measures of phage-caused mortality.
