FIG. 3.

AR1 plaque formation on different preparations of bacteria. The AR1 phage stock was made on the wild-type O157:H7 strain and diluted in a 10-fold series. The phage solutions were then used to infect various preparations of bacteria and plated out on LB agar plates for PFU scoring. When transformed with plasmids, the bacteria were cultivated in the presence of IPTG (1 mM) prior to mixing with the phage. IPTG (1 mM) was also included in the plates used in the plaque assay. No plaque formation was observed with bacteria indicated in columns 2, 3, and 5 through 8. These experiments were repeated three times, with similar results. Wt, wild-type strain.