Induction rate per lysogenic bacteria growing on rich medium (LB).

The induction rate was measured on ampicillin plates by scoring infective centers, as described in the Materials and Methods section. Since bile salts were shown to cause DNA damage in bacteria [34], and to induce a Salmonella prophage [35], we measured their effect on λ induction rate, but no change was detected. Bile salts were added at a final concentration of 0.8%. Mean ± standard deviation of three independent experiments are indicated.