Nutrient Stimulation of Lytic Phage Production in Bacterial Populations of the Gulf of Mexico

The effect of nutrient addition on prophage induction in marine water samples was investigated during a 2001 research cruise in the Gulf of Mexico. To test the hypothesis that prophage induction could be stimulated by nutrient addition, water samples were treated with inorganic and organic nutrients in combination with mitomycin C (1.0 μg ml-1) or with the nutrient alone as controls. An increase in phage abundance was observed at 3 stations in response to additions of PO43- (mesotrophic Mississippi River plume, oligotrophic surface-water, and Dry Tortugas stations), NH4+ (oligotrophic surface-water station), and several organic compounds (oligotrophic surface-water station). Augmented phage production occurred in both the presence and absence of mitomycin C, indicating that inorganic and organic nutrient addition did not appear to stimulate prophage induction. These results suggest that nutrient amendment of environmental samples caused a stimulation of lytic phage production that may have resulted from a stimulation of host-cell growth. However, these results do not preclude nutrient stimulation of prophage induction at other times of the year or in other oceanic environments, which were not examined in this study.