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 ofY. 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 thatY. pestis strain KIM6+, unlike mostEnterobacteriaceae , 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 ofY. 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 theY. pestis SPase for the antibiotic and that alterations to each component of theY. 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 againstY. pestis and potentially other Gram-negative pathogens.