FIG. 4.

Effect of suppression of pbp2 transcription on growth of MRSA strain COL and its isogenic derivative RUSA4 with inactivated mecA gene. Growth of the cultures in liquid medium was monitored by determining the OD₆₂₀. Symbols: ■ and □, COLpPBP2iC-2 grown with and without IPTG, respectively; ▴ and ▵, RUSA4pPBP2iC-2 grown with and without IPTG, respectively. Cultures were allowed to grow until the OD₆₂₀ was approximately 0.2. At that point (indicated by grey and black arrows for RUSA4pPBP2iC-2 and COL pPBP2iC-2, respectively) the IPTG was removed by washing, the cells were resuspended in fresh medium without inducer, and each culture was divided into two portions, only one of which was supplemented with 0.5 mM IPTG. We continued to monitor the OD₆₂₀ after this.