Biochemical and Genetic Characterization of Propionicin T1, a New Bacteriocin from Propionibacterium thoenii

Abstract

ABSTRACT A collection of propionibacteria was screened for bacteriocin production. A new bacteriocin named propionicin T1 was isolated from two strains of Propionibacterium thoenii . This bacteriocin shows no sequence similarity to other bacteriocins. Propionicin T1 was active against all strains of Propionibacterium acidipropionici , Propionibacterium thoenii , and Propionibacterium jensenii tested and also against Lactobacillus sake NCDO 2714 but showed no activity against Propionibacterium freudenreichii . The bacteriocin was purified, and the N-terminal part of the peptide was determined with amino acid sequencing. The corresponding gene pctA was sequenced, and this revealed that propionicin T1 is produced as a prebacteriocin of 96 amino acids with a typical sec leader, which is processed to give a mature bacteriocin of 65 amino acids. An open reading frame encoding a protein of 424 amino acids was found 68 nucleotides downstream the stop codon of pctA . The N-terminal part of this putative protein shows strong similarity with the ATP-binding cassette of prokaryotic and eukaryotic ABC transporters, and this protein may be involved in self-protection against propionicin T1. Propionicin T1 is the first bacteriocin from propionibacteria that has been isolated and further characterized at the molecular level.