FIG 5.

A subset of MPs induces oxidative protein damage in S. aureus. Total protein was extracted from the protoplasts of WT S. aureus (A) or the ΔhrtB S. aureus mutant strain that was grown in the presence or absence of 5 μM MP (B). Representative immunoblots are shown containing protein samples that had been derivatized with DNP (2,4-dinitrophenylhydrazine) to modify sites of oxidative damage. Blots were probed with antibodies specific to the DNP moiety on the proteins. The ladder shown in the image is the Precision Plus Protein All Blue Standard (Bio-Rad). (C) Quantification of immunoblot replicates depicting the fraction of oxidative protein damage in MP-treated samples compared with untreated samples as determined by densitometry. Graphs represent averages of the results determined with at least three independent immunoblots from samples processed on separate days. Error bars represent SEM. The asterisk (*) denotes P < 0.05 as determined by a two-tailed Student's t test.