FIG. 3.

Polymyxin B-mediated outer membrane permeabilization improves the induction of the cspA::lacZ fusion at intermediate chloramphenicol concentrations. ADA310 cultures were grown to mid-exponential phase in LB medium at 37°C. Chloramphenicol was added at the indicated concentrations along with 0.5 μg of polymyxin B sulfate per ml (○) or no additive (•). Clarified extracts were assayed for β-galactosidase activity 3 h after treatment. Error bars correspond to triplicate experiments.