SEASONAL AND DIEL ABUNDANCE OF VIRUSES AND OCCURRENCE OF LYSOGENY BACTERIOCINOGENY IN THE MARINE-ENVIRONMENT/

To understand the role of viruses in the marine environment, it is imp ortant to know the factors affecting their temporal distribution and t he abundance of lysogens. We therefore performed a seasonal and a diel study on viral distribution in Tampa Bay, Florida, USA, and detected the abundance of lysogens and bacteriocinogens amongst marine bacteria l isolates from diverse marine environments. We investigated the distr ibution of viruses, bacterial direct counts, chlorophyll a (chl a), sa linity and temperature during a 13 mo period in the Tampa Bay estuary. The results indicated that the viral population had a strong seasonal pattern with the highest concentrations (2.0 +/- 0.8 x 10(7)) in the summer and lowest (4.8 +/- 1.4 x 10(6)) in the winter. Viral abundance was negatively correlated with salinity (r = -0.803), and positively correlated with chl a concentration (r = 0.725). A diel study in a sea water mesocosm indicated that viral abundance did not vary on a diel r hythm, but rather peaked after a maximum in bacterial abundance and ch l a. Dissolved DNA concentrations displayed diel rhythmicity, suggesti ng that viruses were not the main source of dissolved DNA. An estimati on of the percentage of the bacterial standing stock lysed by viruses based on 4 h intervals ranged from 3.0 to 53.3 % per day. Screening ba cterial isolates for the presence of inducible prophages indicated tha t 43 % were lysogens or bacteriocinogens, suggesting that lysogeny and bacteriocinogeny are common in the marine environment.