title: Identification of a new plasmid-encoded sec-dependent bacteriocin produced by Listeria innocua 743.
abstract: Listeria innocua 743 produces an inhibitory activity demonstrating broad-spectrum inhibition of Listeria monocytogenes isolates. Gel-electrophoretic analysis of culture supernatants indicated that two inhibitors with different molecular weights were produced by this strain. Insertion of Tn917 into a 2.9 Kb plasmid (pHC743) generated mutants with either an impaired ability or a loss in ability to produce one of the inhibitors. Sequence analysis of the transposon insertion regions revealed the presence of two continuous open reading frames, the first encoding a new pediocin-like bacteriocin (lisA) and the second encoding a protein homologous with genes involved in immunity toward other bacteriocins (lisB). Translation of the bacteriocin gene (lisA) initiates from a noncanonical start codon and encodes a 71-amino-acid prebacteriocin which lacked the double glycine leader peptidase processing site common in other type II bacteriocins. Alignment of the sequence with the processed N termini of related bacteriocins suggests that the mature bacteriocin consists of 43 amino acids, with a predicted molecular mass of 4,484 Da. Mutants containing insertions into lisA were sensitive to the inhibitor, indicating that lisAB forms a single operon and that lisB represents the immunity protein. Cloning of an amplicon containing the lisAB operon into Escherichia coli resulted in expression and export of the bacteriocin. This finding confirms that the phenotype is dependent on the structural and immunity gene only and that export of this bacteriocin is sec dependent. This is the first confirmation of bacteriocin production in a Listeria spp., and it is of interest that this bacteriocin is closely related to the pediocin family of bacteriocins produced by lactic acid bacteria.
authors.affiliation: Microbiology Research Division, Bureau of Microbial Hazards, Food Directorate, Health Protection Branch, Health Canada, Banting Research Centre, Tunney's Pasture, Ottawa, Ontario, Canada K1A 0L2. Martin_Kalmokof@hs-sc.gc.ca
authors.forename: M L
authors.initials: ML
authors.lastname: Kalmokoff
authors.forename: S K
authors.initials: SK
authors.lastname: Banerjee
authors.forename: T
authors.initials: T
authors.lastname: Cyr
authors.forename: M A
authors.initials: MA
authors.lastname: Hefford
authors.forename: T
authors.initials: T
authors.lastname: Gleeson
mesh_terms: D000595:Amino Acid Sequence; D001430:Bacteriocins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics* / Q000494:pharmacology; D001483:Base Sequence; D003470:Culture Media; D004251:DNA Transposable Elements; D008087:Listeria / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009876:Operon; D010957:Plasmids / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D001430:Bacteriocins; D003470:Culture Media; D004251:DNA Transposable Elements; C439289:listeriocin 743A