Origins of Yersinia pestis sensitivity to the arylomycin antibiotics and the inhibition of type I signal peptidase.

Yersinia pestis is the etiologic agent of the plague. Reports of Y. pestis strains that are resistant to each of the currently approved first-line and prophylactic treatments point to the urgent need to develop novel antibiotics with activity against the pathogen. We previously reported that Y. pestis strain KIM6+, unlike most Enterobacteriaceae, is susceptible to the arylomycins, a novel class of natural-product lipopeptide antibiotics that inhibit signal peptidase I (SPase). In this study, we show that the arylomycin activity is conserved against a broad range of Y. pestis strains and confirm that it results from the inhibition of SPase. We next investigated the origins of this unique arylomycin sensitivity and found that it does not result from an increased affinity of the Y. pestis SPase for the antibiotic and that alterations to each component of the Y. pestis lipopolysaccharide-O antigen, core, and lipid A-make at most only a small contribution. Instead, the origins of the sensitivity can be traced to an increased dependence on SPase activity that results from high levels of protein secretion under physiological conditions. These results highlight the potential of targeting protein secretion in cases where there is a heavy reliance on this process and also have implications for the development of the arylomycins as an antibiotic with activity against Y. pestis and potentially other Gram-negative pathogens.