A Putative Cro-Like Repressor Contributes to Arylomycin Resistance in Staphylococcus aureus

Abstract

ABSTRACTAntibiotic-resistant bacteria are a significant public health concern and motivate efforts to develop new classes of antibiotics. One such class of antibiotics is the arylomycins, which target type I signal peptidase (SPase), the enzyme responsible for the release of secreted proteins from their N-terminal leader sequences. Despite the essentiality, conservation, and relative accessibility of SPase, the activity of the arylomycins is limited against some bacteria, including the important human pathogenStaphylococcus aureus. To understand the origins of the limited activity againstS. aureus, we characterized the susceptibility of a panel of strains to two arylomycin derivatives, arylomycin A-C16and its more potent analog arylomycin M131. We observed a wide range of susceptibilities to the two arylomycins and found that resistant strains were sensitized by cotreatment with tunicamycin, which inhibits the first step of wall teichoic acid synthesis. To further understand howS. aureusresponds to the arylomycins, we profiled the transcriptional response ofS. aureusNCTC 8325 to growth-inhibitory concentrations of arylomycin M131 and found that it upregulates the cell wall stress stimulon (CWSS) and an operon consisting of a putative transcriptional regulator and three hypothetical proteins. Interestingly, we found that mutations in the putative transcriptional regulator are correlated with resistance, and selection for resistanceex vivodemonstrated that mutations in this gene are sufficient for resistance. The results begin to elucidate howS. aureuscopes with secretion stress and how it evolves resistance to the inhibition of SPase.