There are at least 1030 bacteria on the planet, and there are likely to be at least as many bacterial viruses or bacteriophages attacking them. Given this sheer weight of numbers, the predatory activities of phages should have global significance. Phages are also useful tools for gene transfer, and predicting their behavior under natural conditions is important.
Ashelford et al. over the course of three successive years made field experiments on soil-dwelling bacteria, Serratia liquefaciens, and their bacteriophages in sugar beet plots. Phage-infected bacteria were introduced to the plot. Shortly after inoculation the introduced phage numbers 'bloomed,' but fell dramatically as the sugar beet plants matured. This decline was accompanied by the explosive growth of another, much more virulent naturally occurring bacteriophage. The two phages apparently adopted different replicative strategies to compete for Serratia prey. Thus, a bacterium burdened with a phage can survive in nature as successfully as an uninfected bacterium, and an indigenous microbial community can be altered reproducibly by the release of a bacterium carrying a gene-transducing phage. -- CA