Affiliation:
1. Teagasc Food Research Centre, Moorepark, Fermoy, County Cork, Ireland
2. Alimentary Pharmabiotic Centre, Cork, Ireland
3. Department of Microbiology, University College Cork, Cork, Ireland
Abstract
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. Matrix-assisted 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.
IMPORTANCE
This study describes the identification, purification, and characterization of bactofencin A, a novel type of bacteriocin produced by
L. salivarius
DPC6502. Interestingly, bactofencin A is not similar to any other known bacteriocin but instead shares similarity with eukaryotic cationic antimicrobial peptides, and here, we demonstrate that it inhibits two medically significant pathogens. Genome sequence analysis of the producing strain also revealed the presence of an atypical
dltB
homologue in the bacteriocin gene cluster, which was lacking a classical bacteriocin immunity gene. Furthermore, cloning this gene rendered sensitive strains resistant to the bacteriocin, thereby establishing its role in providing cognate bacteriocin immunity. Four additional
L. salivarius
isolates, also of porcine origin, were found to contain the bacteriocin biosynthesis genes and successfully produced bactofencin A, while these genes were absent from five human-derived strains investigated.
Publisher
American Society for Microbiology
Cited by
49 articles.
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