The SrtA-specific native LPETG substrate incorporation in 8325-4 WT bacteria occurs in a cumulative manner, is growth phase-dependent and negatively correlates to the srtA mRNA expression.

<p>(A) Native LPETG substrate incorporation during different bacterial growth phases. <i>S. aureus</i> 8325-4 WT and <i>srtA</i> KO were grown until different growth phases (exp: exponential, post log: post-logarithmic, stat: stationary or late stationary) in the presence of 1 mM native or scrambled LPETG substrates. Bacteria were harvested at several time points depicted on the x-axis. The mean fluorescence intensity is depicted on the y-axis. (B) Determination of the SrtA activity towards the native LPETG substrate in <i>S. aureus</i> bacteria in different bacterial growth phases. Five WT <i>S. aureus</i> strains and one <i>S. aureus srtA</i> KO strain were cultured in LB medium in the absence of the substrate until exponential, post-logarithmic, stationary or late stationary phase. Normalized bacteria to OD_{600 nm} 0.5 were incubated with the native or scrambled LPETG substrate in SrtA buffer during 1 hr. The bacteria were analysed with FACS after several PBS washes. Bacteria tested are depicted on the x-axis and the mean fluorescence intensity is depicted on the y-axis. We used one-way ANOVA testing with Bonferroni correction to analyse statistical differences. (C) Determination of the <i>srtA</i> expression during different growth phases. 8325-4 WT and O1 <i>S. aureus</i> strains were cultured until the previously mentioned growth phases at which mRNA was isolated. The time points at which the bacteria were harvested are plotted on the x-axis. The mean fluorescence reflecting the native LPETG substrate incorporation in the corresponding strains was plotted for the comparison on the right y-axis. The mRNA transcripts are depicted on the left y-axis. <i>srtA</i> transcripts were quantified and compared to the transcription of <i>gyr</i>B.