Isolation, partial characterization and mode of action of acidocin J1229, a bacteriocin produced by Lactobacillus acidophilus JCM 1229

Lactobacillus acidophilus JCM 1229 produces a heat‐stable bacteriocin, designated as acidocin J1229, that has a narrow inhibitory spectrum. Production of acidocin J1229 in MRS broth was pH dependent, with maximum activity detected in broth culture maintained at pH 5:0. Acidocin J1229 was purified by ammonium sulphate precipitation and sequential cation exchange and reversed‐phase chromatographies. The sequence of the first 24 amino acid residues of the N terminus of acidocin J1229 was determined. The molecular mass of acidocin J1229 as determined by mass spectrometry was 6301 Da. Acidocin J1229 showed a bactericidal effect but not a bacteriolytic effect on sensitive cells. Acidocin J1229 dissipated the membrane potential and the pH gradient in sensitive cells, which affected such proton motive force‐dependent processes as amino acid transport. Acidocin J1229 also caused an efflux of glutamate, previously taken up via a unidirectional ATP‐driven transport system. Secondary structure prediction revealed the presence of an amphiphilic a‐helix region that could form hydrophilic pores. These results suggest that acidocin J1229 is a pore‐forming peptide that creates cell membrane channels through the ‘barrel‐stave’mechanism.