Genetic diversity and population dynamics of cyanophage communities in the Chesapeake Bay

In order to understand the genetic diversity and population dynamics of cyanophages in estuarine waters, the viral capsid assembly (g20) gene was used as a gene marker to monitor genetic variations of natural cyanomyovirus communities in the Chesapeake Bay, USA. Unique and diverse g20 sequences were found. Only 1 of 15 g20 genotypes was closely related to the known cyanomyovirus isolates. Most of the g20 genotypes in the bay were not related to the g20 clonal sequences recovered from open-ocean waters. Terminal-restriction fragment length polymorphism (T-RFLP) based on the g20 gene was developed to investigate spatial and temporal distribution of cyanomyovirus communities in the bay. The T-RFLP profiles of the g20 gene demonstrated that the cyanomyovirus population structures in the bay were more dynamic seasonally than spatially. Seasonal variation in the cyanophage community appeared to correspond to changes in host-cell density, which in turn was mainly affected by water temperature. This study represents the first effort to monitor both cyanophage titer and genetic diversity over time and space. The results of our study suggest that cyanophages could play a significant role in regulating Synechococcus biomass and population structure in the Chesapeake Bay.