The antibacterial action of microcin J25: evidence for disruption of cytoplasmic membrane energization in Salmonella newport

Abstract

Microcin J25 (MccJ25) is a cyclic peptide of 21 unmodified amino acid residues produced by a fecal strain of Escherichia coli. It has previously been shown that the antibiotic activity of this peptide is mainly directed to Enterobacteriaceae, including several pathogenic E. coli, Salmonella and Shigella strains. In this paper we show that MccJ25 acts on the cytoplasmic membrane of Salmonella newport cells producing alteration of membrane permeability, and the subsequent gradient dissipation, that initiate the inhibition of process, such as oxygen consumption. These results, taken together with our in vitro observations [Rintoul et al. (2000) Biochim. Biophys. Acta 1509, 65–72], strongly suggest that the disruption of the cytoplasmic membrane gradient is closely related to the bactericidal activity of MccJ25 in S. newport.