FIG. 1.

Expression of β-lactamase from the norA promoter in a transcriptional fusion in S. aureus RN6390, SH1000, SH1000 (mgrA), and RN6390 (mgrA). (A) The β-lactamase activities were normalized to that of the strains carrying the vector alone (pWN2018). The β-lactamase activities are expressed in micromoles of nitrocephin hydrolyzed per milligram of cell protein per minute, and each assay was done in triplicate (values represent means and the error bars the standard deviations). In pBF8-30, the norA promoter was cloned upstream of the β-lactamase gene of plasmid pWN2018. (B) RT-PCRs using RNA extracted at the exponential phase. Each reaction used 10 picograms of total RNA as template and primers specific to an internal region of norA.