Figure 3. Infectious phage in the supernatants of Shiga toxin 1a gene (stx1a)–encoding Shigella flexneri are induced with mitomycin C (mito C) treatment. Supernatants were collected from exponential cultures of BS937, BS938, and BS974 grown with or without 0.5 μg/mL mito C for 3 h. The number of infectious phage particles was determined by a soft agar overlay method that used Escherichia coli MG1655 as the recipient. Plaque forming units (PFUs) of phage lysate were counted after 24 h incubation. Data are averages of 3 independent experiments. Error bars indicate standard error.