FIGURE 1.

The genome of bacteriophage A25 reveals an escape from lysogeny. The 33,900-bp generalized transducing phage A25 is shown. The portion of the chromosome included in the shaded box is the high homology region that contains the remnant lysogeny module and other genes that A25 shares with prophages from genome strains MGAS10270 (M2), MGAS315 (M3), MGAS10570 (M4), and STAB902 (M4). Unlike these complete lysogens, A25 only has the operator and antirepressor from the lysogeny module (shown in expanded view below the map), apparently having lost the integrase and repressor for lysogeny some time in the past. This A25 expanded region is compared to the homologous region from genome prophage MGAS10270.2, which contains these elements as well as the upstream genes including the cI-like repressor. Promoters are shown as directional arrows. Introduction of the MGAS10270.2 repressor into an A25-sensitive S. pyogenes strain results in its conversion to a high level of A25 resistance (32). The genome follows a typical modular arrangement, with the predicted function for A25 genes indicated by color: regulation, dark red; DNA replication, pink; encode endonucleases, dark blue; genome packaging, light blue; structural, green; and lysis, yellow. The figure is redrawn from McCullor et al. (32).