Acidocin A, a bacteriocin produced by Lactobacillus acidophilus TK9201, is active against closely related lactic acid bacteria and food-borne pathogens including Listeria monocytogenes. The bacteriocin was purified to homogeneity by ammonium sulfate precipitation and sequential ion-exchange and reversed-phase chromatographies. The molecular mass was determined by high-performance liquid chromatography gel filtration to be 6,500 Da. The sequence of the first 16 amino acids of the N terminus was determined, and oligonucleotide probes based on this sequence were constructed to detect the acidocin A structural gene acdA. The probes hybridized to the 4.5-kb EcoRI fragment of a 45-kb plasmid, pLA9201, present in L. acidophilus TK9201, and the hybridizing region was further localized to the 0.9-kb KpnI-XbaI fragment. Analysis of the nucleotide sequence of this fragment revealed that acidocin A was synthesized as an 81-amino-acid precursor including a 23-amino-acid N-terminal extension. An additional open reading frame (ORF2) encoding a 55-amino-acid polypeptide was found downstream of and in the same operon as acdA. Transformants containing this ORF2 became resistant to acidocin A, suggesting that ORF2 encodes an immunity function for acidocin A. The 7.2-kb SacI-XbaI fragment containing the upstream region of acdA of pLA9201 was necessary for acidocin A expression in the acidocin A-deficient mutant, L. acidophilus TK9201-1, and other Lactobacillus strains.
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 ␣ and . On the basis of N-terminal amino acid sequencing and the molecular masses of the ␣ and  components, it is interpreted that the compounds differ by an additional glycine residue in the  component. Both ␣ and  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 ␣-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.
T. TAHARA AND K. KANATANI. 1996. Lactobacillus acidophilus JCM 1229 produces a heatstable bacteriocin, designated as acidocin J1229, that has a narrow inhibitory spectrum. Production of acidocin J1229 in MRS broth was p H dependent, with maximum activity detected in broth culture maintained at p H 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 51229 was determined. T h e molecular mass of acidocin J1229 as determined by mass spectrometry was 6301 Da. Acidocin 51229 showed a bactericidal effect but not a bacteriolytic effect on sensitive cells. Acidocin J1229 dissipated the membrane potential and the p H gradient in sensitive cells, which affected such proton motive force-dependent processes as amino acid transport.Acidocin 51229 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 51229 is a pore-forming peptide that creates cell membrane channels through the 'barrel-stave' mechanism.
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 alpha-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.
Acidocin 8912 is a bacteriocin produced by Lactobacillus acidophilus TK8912. The acidocin 8912 structural gene, acdT, was cloned and determined. It was located on the 14-kb plasmid pL103 and encoded a 46 amino acid precursor including a 20 amino acid N-terminal extension. The precursor sequence of the acdT gene shows a conservation of the general structural characteristics of the bacteriocin precursors from some lactic acid bacteria.
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