FIG. 5.
Roles of DNA supercoiling and RecA activity in the salt-dependent increase in spontaneous induction of λimm434 prophage. Phage-containing supernatants were obtained from wild-type or recA mutant MG1655 cells lysogenized with λimm434 bacteriophage grown for 5 h without or with 200 mM of added NaCl. For experiments done in the presence of novobiocin, cells were grown in the presence of 80 μg/ml novobiocin as described in Materials and Methods. The effect of salt shock on phage production is expressed as the number of phage produced per viable cell incubated in the presence of salt divided by the number of phage produced per viable cell in the absence of added salt. Note the logarithmic scale of the y axis. The error bars indicate standard deviations.