Isolation, partial characterization, and mode of action of acidocin J1132, a two-component bacteriocin produced by Lactobacillus acidophilus JCM 1132

Abstract

Lactobacillus acidophilus JCM 1132 produces a heat-stable, two-component bacteriocin designated acidocin J1132 that has a narrow inhibitory spectrum. Maximum production of acidocin J1132 in MRS broth was detected at pH 5.0. Acidocin J1132 was purified by ammonium sulfate precipitation and sequential cation exchange and reversed-phase chromatographies. Acidocin J1132 activity was associated with two components, termed α and β. On the basis of N- terminal amino acid sequencing and the molecular masses of the α and β components, it is interpreted that the compounds differ by an additional glycine residue in the β component. Both α and β had inhibitory activity, and an increase in activity by the complementary action of the two components was observed. Acidocin J1132 is bactericidal and dissipates the membrane potential and the pH gradient in sensitive cells, which affect such proton motive force-dependent processes as amino acid transport. Acidocin J1132 also caused efflux of preaccumulated amino acid taken up via a unidirectional ATP- driven transport system. Secondary structure prediction revealed the presence of an amphiphilic α-helix region that could form hydrophilic pores. These results suggest that acidocin J1132 is a pore-forming bacteriocin that creates cell membrane channels through the 'barrel-stave' mechanism.