Staphylococcus aureus continues to exert significant pressure upon public-health in Australia, both in the clinic and the community. Molecular dissection of systems essential for staphylococcal viability can provide valuable intelligence in the search for new strategies to combat this pathogen. One such system is WalKR; the only essential two-component regulator in S. aureus. In addition to a role in maintaining cell wall homeostasis, the walKR locus is a hotspot for mutations conferring resistance to last-line antibiotics. Despite the importance of this system its regulon is not well defined, and a robust explanation of its essentiality is yet to be elucidated.
Here, we use a functional genomics approach to interrogate a panel of WalKR ‘up’ and ‘down’ mutants, using data from ChIPseq and RNAseq to define a WalR binding motif and characterise the direct regulon of WalKR. In addition to controlling several autolysins involved in cell wall homeostasis, it appears that WalR mediates direct control of genes involved in a variety of other cellular processes, some of which are essential. Subsequently, we employed fluorescence-based promoter reporters, electrophoretic mobility shift assays, and Western blot analysis, to validate our initial observations. Our results provide new insights into the essentiality of WalKR, and ultimately may lead to novel methods for disrupting this system.