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 maxim um activity detected in broth culture maintained at pH 5.0. Acidocin J 1229 was purified by ammonium sulfate precipitation and sequential cat ion exchange and reversed-phase chromatographies. The sequence of the first 24 amino acid residues of the N terminus of acidocin J1229 was d etermined. 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 diss ipated the membrane potential and the pH gradient in sensitive cells, which affected such proton motive force-dependent processes as amino a cid transport. Acidocin J1229 also caused an efflux of glutamate, prev iously taken up via a unidirectional ATP-driven transport system. Seco ndary structure prediction revealed the presence of an amphiphilic alp ha-helix region that could form hydrophilic pores. These results sugge st that acidocin J1229 is a pore-forming peptide that creates cell mem brane channels through the 'barrel-stave' mechanism.