FIG 5.

CcpA directly regulates cidABC expression by binding to the cre site within the cidA promoter. (A) EMSA was performed using increasing concentrations of purified CcpA protein (100 to 7,000 nM) and biotin-labeled wild-type cidA promoter DNA as a target. Reaction mixtures were incubated for 30 min at room temperature and separated on a 6% TBE polyacrylamide gel. Lanes 1 and 9 contain a no-protein control and a 200-fold excess of unlabeled competitor DNA control, respectively. (B) Effect of cre site presence on cidABC expression. S. aureus cultures with lacZ reporter plasmids containing cidA promoter DNA fragment with native or mutated (cre*) cre site were grown in plain TSB or TSB medium supplemented with 35 mM glucose. After 6 h of growth, samples were collected and assayed for β-galactosidase activity. Statistical significance between the wild‐type strain grown in plain TSB and wild‐type strain (*) or pta mutant (**) grown under inducing conditions was determined by Student's t test (P ≤ 0.001).