FIGURE 1.

The peptide encoded by SprA1, PepA1, inhibits S. aureus growth and induces death by membrane permeabilization. A, comparative growth curves, after aTc induction, of strain Newman containing either an empty pAT12 plasmid (triangles), pAT12ΩSprA1 (squares), or pAT12ΩsprA1-STOP (circles). B, serial dilutions of strain Newman containing empty pAT12, pAT12ΩsprA1, or pAT12ΩsprA1-STOP, deposited on medium containing 1 μm aTc, and incubated overnight. C, pictures of fluorescent-labeled S. aureus cells after LIVE/DEAD experiments demonstrating that PepA1 encoded by SprA1 induces S. aureus death. Newman cells containing empty pAT12 plasmid are alive (green fluorescence), whereas those containing pAT12ΩsprA1 have damaged membranes (red fluorescence). Most cells containing pAT12ΩsprA1-STOP are alive. S. aureus living cells were counted for each of the three constructs, and the results are expressed as percentages of living cells. The error bars correspond to standard deviations inferred from three independent experiments. D, Northern blot detection of SprA1 RNA levels in the three strains before (−) and after (+) a 1-h induction with 1 μm aTc.