FIG. 6.

Expression is heterogeneous in different strains of S. pyogenes. HSC5 (A) and MGAS166s (B) demonstrate two distinct patterns of prtF expression. These hosts were used to analyze the PhoZF activity of selected prtF promoter mutants (Fig. 4). The bars indicate activity expressed as a percentage of that obtained from JRS4(pMGC66), which contains the entire rofA-prtF intergenic region, when the indicated strains were cultured aerobically (solid bars) or anaerobically (hatched bars). “No Plasmid” indicates the background activity of the host under analysis in the absence of any plasmid. Note that in contrast to JRS4, expression of prtF is stimulated by aerobic growth in both HSC5 and MGAS166s. However, while prtF expression is preferentially stimulated only under aerobic conditions in HSC5, high levels of expression are obtained under both anaerobic and aerobic conditions in MGAS166s, with levels considerably higher than those demonstrated by JRS4 under either condition. Despite these differences and in contrast to JRS4, elimination of either the proximal or distal region of the large RofA binding site (pPro9 or pPro10, respectively) greatly reduces expression in both HSC5 and MGAS166s under all conditions analyzed. Data represent the means and standard errors of the means for at least three independent experiments, each conducted in duplicate.