A metagenomic examination of a solar saltern in Southern California

The species composition and metabolic potentials of microbial communities appear to be predictable and stable for any particular ecosystem. This apparent stability contradicts theoretical models and experiments of viral-microbial dynamics, which show Kill-the-Winner behavior (i.e., rapid cycling of strains of microbes and their viral predators).;Here metagenomic time-series from four aquatic environments were used to resolve this apparent paradox. Each environment had a characteristic species composition and metabolic potential that was stable over time. In contrast, there were rapid changes at the level of viral genotypes and microbial strains. Together these results suggest a model where functional groups of microbes are constant features of an environment and underlying this stability is a dynamic equilibrium of microbial strains and viral genotypes. This model was investigated further by comparing community metabolism as defined by the metagenome with the predicted metabolic potentials of different species. Consistent with the model, the top-ranked species were the best predictors of the metabolic capabilities of the communities.;Overall, these results show that a dynamic equilibrium of functionally-redundant microbial and viral strains continuously replace each other in a Kill-the-Winner fashion, thus maintaining a stable metabolic potential and taxonomical signal.