Attachment and replication of Pseudomonas aeruginosa bacteriophages under conditions simulating aquatic environments

Bacterial viruses are important in regulating bacterial population densities in natural aquatic environments, but the dynamics of bacteriophage-bacterial interactions in nature are poorly understood. In this study, the attachment and replication of three Pseudomonas aeruginosa bacteriophages (one temperate and two virulent) were investigated under conditions similar to those found in nature. Attachment and replication of bacteriophages were not impaired at host-cell densities equal to or lower (< 105 c.f.u. ml-1) than those frequently found in aquatic environments when the host cells were physiologically competent to allow phage growth. Attachment (45–93%) to either actively growing or starved cells was not impaired in river water, indicating that attachment is efficient in natural freshwater habitats. However, the replication of bacteriophages was significantly altered in starved cells in river water: the latency period was extended (broth, 70–110 min; river water, 110–240 min), and the burst size was reduced (broth, 27–65; river water 5–7). The findings of this study indicate that phages are likely to affect microbial ecology significantly in freshwater ecosystems.