EFFECTS OF VIRUSES ON NUTRIENT TURNOVER AND GROWTH EFFICIENCY OF NONINFECTED MARINE BACTERIOPLANKTON

The effects of virus infection and lysis of a marine Vibrio sp, on C, N, and P turnover and the growth efficiency of noninfected bacteriopla nkton were studied in a series of dilution cultures. The cultures were enriched with various sources of organic matter and N and P. The grow th of the Vibrio host and the growth of the natural bacterioplankton w ere measured by immunofluorescence and 4',6-diamidino-2-phenylindole s taining methods, respectively. Lysis products resulting from infection of the Vibrio sp, caused an increase in metabolic activity and cell p roduction by the noninfected bacterioplankton. In P-limited cultures, the addition of viruses increased the uptake of dissolved organic carb on by 72% and the potential alkaline phosphatase activity by 89% compa red with control cultures without viruses. Our data suggest that input of available phosphorus through virus-induced Vibrio lysates occurred , which caused an increase in the bacterial nutrient uptake, The growt h efficiency of noninfected bacteria was reduced in the presence of vi ruses compared with the control without viruses (growth efficiencies, 0.08 +/- 0.03 and 0.24 +/- 0.02, respectively). We suggest that the de crease in growth efficiency may be explained by an increase in bacteri al energy demand associated with extracellular degradation of polymeri c organic nitrogen and phosphorus in cell lysates.