Figure 1.

The lytic and lysogenic pathways of bacteriophages. In the lysogenic pathway, the phage genome (thick line) is shown integrated into the bacterial genome. Bacterial genome projects have revealed that, on average, there are 2.5 phage genomes per bacterium. In the case of Streptococcus pyogenes (154-157) and Escherichia coli O157:H7 (158,159), the bacterial genomes contain multiple phage genomes. The reversion to the lytic state (‘induction’) occurs spontaneously but can be enhanced by certain chemical and antibiotics (160,161)