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Bactofencin A, a New Type of Cationic Bacteriocin with Unusual Immunity
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29/10/2013
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e00498-13.full.pdf
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O’Shea EF, O’Connor PM, O’Sullivan O, Cotter PD, Ross RP, Hill C. 2013. Bactofencin A, a new type of cationic bacteriocin with unusual immunity. mBio 4(6):e00498-13. doi:10.1128/mBio.00498-13
Abstract
Bacteriocin production is an important probiotic trait of intestinal bacteria. In this study, we identify a new type of
bacteriocin, bactofencin A, produced by a porcine intestinal isolate Lactobacillus salivarius DPC6502, and assess its potency
against pathogenic species including Staphylococcus aureus and Listeria monocytogenes. Genome sequencing of the bacteriocin
producer revealed bfnA, which encodes the mature and highly basic (pI 10.59), 22-amino-acid defensin-like peptide. Matrixassisted
laser desorption ionization–time of flight (MALDI-TOF) mass spectral analysis determined that bactofencin A has a molecular
mass of 2,782 Da and contains two cysteine residues that form an intramolecular disulfide bond. Although an ABC transporter
and transport accessory protein were also present within the bacteriocin gene cluster, a classical bacteriocin immunity
gene was not detected. Interestingly, a dltB homologue was identified downstream of bfnA. DltB is usually encoded within the dlt
operon of many Gram-positive bacteria. It is responsible for D-alanylation of teichoic acids in the cell wall and has previously
been associated with bacterial resistance to cationic antimicrobial peptides. Heterologous expression of this gene conferred bactofencin
A-specific immunity on sensitive strains of L. salivarius and S. aureus (although not L. monocytogenes), establishing its
role in bacteriocin immunity. An analysis of the distribution of bfnA revealed that it was present in four additional isolates derived
from porcine origin and absent from five human isolates, suggesting that its distribution is host specific. Given its novelty,
we anticipate that bactofencin A represents the prototype of a new class of bacteriocins characterized as being cationic, with a
DltB homologue providing a cognate immunity function.