Seasonal variations in the community structure of actively growing bacteria in neritic waters of Hiroshima Bay, western Japan.

Using bromodeoxyuridine (BrdU) magnetic beads immunocapture and a PCR-denaturing gradient gel electrophoresis (DGGE) technique (BUMP-DGGE), we determined seasonal variations in the community structures of actively growing bacteria in the neritic waters of Hiroshima Bay, western Japan. The community structures of actively growing bacteria were separated into two clusters, corresponding to the timing of phytoplankton blooms in the autumn-winter and spring-summer seasons. The trigger for changes in bacterial community structure was related to organic matter supply from phytoplankton blooms. We identified 23 phylotypes of actively growing bacteria, belonging to Alphaproteobacteria (Roseobacter group, 9 phylotypes), Gammaproteobacteria (2 phylotypes), Bacteroidetes (8 phylotypes), and Actinobacteria (4 phylotypes). The Roseobacter group and Bacteroidetes were dominant in actively growing bacterial communities every month, and together accounted for more than 70% of the total DGGE bands. We revealed that community structures of actively growing bacteria shifted markedly in the wake of phytoplankton blooms in the neritic waters of Hiroshima Bay.