Effects of transposon insertion in ahpC unexplained by polarity of transposon insertion.
(A) Cultures of S. aureus wild-type, Δagr mutant, and various double mutants were treated with H2O2 (20 mM for 60 min) prior to measurement of survival. For strain descriptions, see SI Appendix, Table S2. (B) ahpC locus map showing the three ORFs located downstream of ahpC. The location of four Bursa aurealis insertions (NE911, NE1571, NE537, NE725), obtained from The Nebraska Transposon Mutant Library (NTML) (53) used in this study are indicated by triangles. Green triangles, plus-strand insertion; red triangle, minus-strand insertion. Data represent the means ± S.D. from biological replicates (n = 3). Bacterial strains were BS435 for WT and BS1010, BS1494, BS1504, BS1495, BS1501, BS1496 and BS1506 for the agr, ahpF, SAUSA300_0377, and SAUSA300_0378 mutants, respectively.
Since the Bursa aurealis (bursa) transposon insertion in ahpC was upstream of several open reading frames (ORFs) in the ahpC-F operon, polarity could complicate interpretation of the results. We therefore analyzed the effects of the three bursa mutants in strain JE2 downstream genes: ahpF, SAUSA300_0378, SAUSA300_0377. We found that polar effects on downstream elements could not explain the properties of ahpC::bursa. Thus, ahpC::bursa could provide insights into the role of ahpC in agr-mediated phenotypes.