Fig 2.
Tests of P3 promoter activity in congenic strains containing unique agr alleles. S. aureus cells of the 8325-4 (A, C) or Newman (B, D) background containing the indicated agr allele (at SaPI-1 attC) and a chromosomal agrp3-blaZ transcriptional fusion (ϕ11 attB∷pEG835) were assayed for β-lactamase activity during growth in triplicate cultures. (C, D) agr-x-y refers to chimeric agr loci, with x representing the 5′ fragment containing RNAIII and the intergenic region, and y representing the 3′ fragment containing agrBDCA (see Fig. S1 in the supplemental material). (E, F) Effect of exogenous AIP on agrp3 activity. S. aureus cells derived from strain Newman containing agr-III (E) or agr-I (F) and the agrp3-blaZ reporter were assayed before or after addition at the indicated time points of AIP at 1 μM. Assay data are presented as β-lactamase units ± standard errors of the means (SEM) (closed symbols, left axis) and growth as optical density measurements (gray open symbols, right axis).