Investigation of the Staphylococcus aureus GraSR Regulon Reveals Novel Links to Virulence, Stress Response and Cell Wall Signal Transduction Pathways
Figure 4
GraSR-dependent gene expression requires GraX, colistin and the consensus binding site.
vraFG (A) and mprF (B) expression was followed using transcriptional lacZ fusions, with or without the upstream GraR operator sequence (vraF'-lacZ, mprF'-lacZ and ΔAvraF'-lacZ, ΔAmprF'-lacZ, respectively). The fusions were introduced in S. aureus strains HG001, ST1036 (ΔgraRS) and ST1070 (ΔgraX). Expression was measured during mid-exponential growth in TSB at 37°C (grey bars) or after treatment with 50 µg ml−1 colistin (black bars). β-Galactosidase assays were performed as described in Materials and Methods. Means and standard deviation values are presented from three independent experiments.