Effect of murF gene conditional expression on beta-lactam resistance. (A) Oxacillin inhibition halos (1-mg disks) were determined for COL and COLspacmurF grown under IPTG concentrations of 100, 10, 7.5, 5.0, 2.5, and 0 μM. (B) Ceftizoxime inhibition halos (30-μg disks) were determined for ZOX3 and ZOX3spacmurF grown under IPTG concentrations of 100, 10, 7.5, 5.0, and 2.5 μM.