Community Interactions and Nutrient Concentrations Affect Diel Periodicity of Microbial Gene Expression in Oligotrophic Sunlit Waters.

Previous work across decades has demonstrated 24-hour periodicity in the timing of many cellular activities across the pelagic marine microbial community. In previous work, temporal staggering of peak times of periodic gene expression by different taxonomic groups has been hypothesized to be the result of a metabolic cascade of food web interactions. We further this hypothesis with evidence of impacts of nutrient concentrations and community on the 24-hour periodicity of specific transcript levels. Diel transcriptomic studies across vertical (from the surface to the base of the euphoric zone) and horizontal (cyclonic and anticyclonic mesoscale eddys) gradients in the North Pacific Subtropical Gyre (NPSG) revealed a relationship between Nitrogen concentrations and amount of transporter gene expression periodicity in Prochlorococcus. Comparison of whole NPSG water mesocosm light perturbation experiments to previous isolate culture studies demonstrated an effect of community presence on periodic behaviors of individual taxa. The demonstrated influence of community and nutrient concentrations on the diel regulation of gene expression by microbes provides evidence for a connection between periodicity and nutrient exchange between taxa. Together, these studies contribute to an emerging view of the highly interconnected and temporally phased nature of microbial communities, especially in low-nutrient environments such as the open ocean euphotic zone.