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Molecular and genetic characterization of a novel bacteriocin locus in Enterococcus avium isolates from infants.

ABSTRACT: Enterococci are among the most common human intestinal lactic acid bacteria, and they are known to produce bacteriocins. In this study, fecal enterococci were isolated from infants and screened for bacteriocin production. Bacteriocin-producing Enterococcus avium isolates were obtained, and a new pediocin-like bacteriocin was purified and characterized. This bacteriocin, termed avicin A, was found to be produced by isolates from two healthy infants. It was purified to homogeneity from culture supernatant by ion-exchange and reversed-phase chromatography, and part of its amino acid sequence was obtained. The sequence of a 7-kb DNA fragment of a bacteriocin locus was determined by PCR and DNA sequencing. The bacteriocin locus was organized into four operon-like structures consisting of (i) the structural genes encoding avicin A and its immunity protein, (ii) a divergicin-like bacteriocin (avicin B) gene, (iii) an ABC bacteriocin transporter gene and two regulatory genes (histamine protein kinase- and response regulator-encoding genes), and (iv) induction peptide pheromone- and transport accessory protein-encoding genes. It was shown that the production of avicin A was regulated by the peptide pheromone-inducible regulatory system. Avicin A shows very high levels of similarity to mundticin KS and enterocin CRL35. This bacteriocin showed strong antimicrobial activity against many species of Gram-positive bacteria, including the food-borne pathogen Listeria monocytogenes. The avicin A locus is the first bacteriocin locus identified in E. avium to be characterized at the molecular level.

SUBMITTER: Birri DJ

PROVIDER: S-EPMC2805230 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature

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Molecular and genetic characterization of a novel bacteriocin locus in Enterococcus avium isolates from infants.

Birri Dagim Jirata DJ Brede Dag A DA Forberg Torunn T Holo Helge H Nes Ingolf F IF

Applied and environmental microbiology 20091120 2

Enterococci are among the most common human intestinal lactic acid bacteria, and they are known to produce bacteriocins. In this study, fecal enterococci were isolated from infants and screened for bacteriocin production. Bacteriocin-producing Enterococcus avium isolates were obtained, and a new pediocin-like bacteriocin was purified and characterized. This bacteriocin, termed avicin A, was found to be produced by isolates from two healthy infants. It was purified to homogeneity from culture sup ...[more]

PMID: 19933345

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Project description:Bacteriocin 51 (Bac 51) is encoded on the mobile plasmid pHY (6,037 bp), which was isolated from vancomycin-resistant Enterococcus faecium VRE38. Bacteriocin 51 is active against E. faecium, E. hirae, and E. durans. Sequence analysis of pHY showed that it encodes nine open reading frames (ORFs) from ORF1 to ORF9 (in that order). Genetic analysis suggested that ORF1 and ORF2, which were designated bacA and bacB, respectively, are the bacteriocin and immunity genes. bacA encodes a 144-amino-acid protein. The deduced BacA protein has a typical signal sequence at its amino terminus, and a potential signal peptidase-processing site corresponding to the V-E-A sequence is located between the 37th and 39th amino acids. The predicted mature BacA protein consists of 105 amino acids. A potential promoter sequence was identified upstream of the start codon. bacB encodes a 55-amino-acid protein. No obvious promoter or terminator sequence was identified between bacA and bacB. Northern blot analysis of bacA and bacB with a bacA RNA probe produced a transcript of approximately 700 nucleotides, which corresponded to the combined nucleotide sizes of bacA and bacB, indicating that transcription was initiated from the promoter upstream of bacA, continued through bacB, and was terminated at the terminator downstream of bacB. The transcription start site was determined to be the T nucleotide located 6 nucleotides downstream from the -10 promoter sequence. These results indicate that bacA and bacB constitute an operon and that bacA is the bacteriocin structural gene while bacB is the immunity gene. The purified C-terminally His tagged BacA protein of Bac 51 showed bacteriostatic activity against the indicator strain. The purified C-terminally His tagged BacA protein of Bac 32 (whose mature BacA protein has 54 amino acids) and the culture filtrates of the Bac 31- and Bac 43-producing E. faecalis strain FA2-2 showed bactericidal activity. Bac 31 and Bac 43 are pore-forming bacteriocins, unlike the newly characterized bacteriocin Bac 51.

Dataset Information

Molecular and genetic characterization of a novel bacteriocin locus in Enterococcus avium isolates from infants.

Publications

Molecular and genetic characterization of a novel bacteriocin locus in Enterococcus avium isolates from infants.

Similar Datasets

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