• Bactofencin A, a New Type of Cationic Bacteriocin with Unusual Immunity

      O'Shea, Eileen F.; O'Connor, Paula M.; O'Sullivan, Orla; Cotter, Paul D.; Ross, R Paul; Hill, Colin; Department of Agriculture, Food and the Marine, Ireland; Science Foundation Ireland; 04R; 07/CE/B1368 (American Society for Microbiology, 29/10/2013)
      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.
    • Production of bioactive substances by intestinal bacteria as a basis for explaining probiotic mechanisms: Bacteriocins and conjugated linoleic acid

      O'Shea, Eileen F.; Cotter, Paul D.; STANTON, CATHERINE; Ross, R Paul; Hill, Colin; Department of Agriculture, Food and the Marine, Ireland; Science Foundation Ireland; 04R & DC; 07/CE/B1368 (Elsevier Science B.V., 16/01/2012)
      The mechanisms by which intestinal bacteria achieve their associated health benefits can be complex and multifaceted. In this respect, the diverse microbial composition of the human gastrointestinal tract (GIT) provides an almost unlimited potential source of bioactive substances (pharmabiotics) which can directly or indirectly affect human health. Bacteriocins and fatty acids are just two examples of pharmabiotic substances which may contribute to probiotic functionality within the mammalian GIT. Bacteriocin production is believed to confer producing strains with a competitive advantage within complex microbial environments as a consequence of their associated antimicrobial activity. This has the potential to enable the establishment and prevalence of producing strains as well as directly inhibiting pathogens within the GIT. Consequently, these antimicrobial peptides and the associated intestinal producing strains may be exploited to beneficially influence microbial populations. Intestinal bacteria are also known to produce a diverse array of health-promoting fatty acids. Indeed, certain strains of intestinal bifidobacteria have been shown to produce conjugated linoleic acid (CLA), a fatty acid which has been associated with a variety of systemic health-promoting effects. Recently, the ability to modulate the fatty acid composition of the liver and adipose tissue of the host upon oral administration of CLA-producing bifidobacteria and lactobacilli was demonstrated in a murine model. Importantly, this implies a potential therapeutic role for probiotics in the treatment of certain metabolic and immunoinflammatory disorders. Such examples serve to highlight the potential contribution of pharmabiotic production to probiotic functionality in relation to human health maintenance.
    • Production of multiple bacteriocins from a single locus by gastrointestinal strains of Lactobacillus salivarius

      O'Shea, Eileen F.; O'Connor, Paula M.; Raftis, Emma J.; O'Toole, Paul W.; STANTON, CATHERINE; Cotter, Paul D.; Ross, R Paul; Hill, Colin; Department of Agriculture, Food and the Marine, Ireland; Science Foundation Ireland; et al. (American Society for Microbiology, 07/10/2011)
      Bacteriocins produced by Lactobacillus salivarius isolates derived from gastrointestinal origin have previously demonstrated efficacy for in vivo protection against Listeria monocytogenes infection. In this study, comparative genomic analysis was employed to investigate the intraspecies diversity of seven L. salivarius isolates of human and porcine intestinal origin, based on the genome of the well characterised bacteriocin-producing strain L. salivarius UCC118. This revealed a highly conserved megaplasmid-encoded gene cluster in these strains involved in the regulation and secretion of two-component class IIb bacteriocins. However, considerable intraspecific variation was observed in the structural genes encoding the bacteriocin peptides. These ranged from close relatives of abp118 such as salivaricin P, which differs by 2 amino acids, to completely novel bacteriocins such as salivaricin T, which is characterized in this study. Salivaricin T inhibits closely related lactobacilli and bears little homology to previously characterized salivaricins. Interestingly, the two peptides responsible for salivaricin T activity, SalTα and SalTβ, share considerable identity with the component peptides of thermophilin 13, a bacteriocin produced by Streptococcus thermophilus. Furthermore, the salivaricin locus of strain DPC6488 also encodes an additional novel one-component class IId anti-listerial bacteriocin, salivaricin L. These findings suggest a high level of redundancy in the bacteriocins that can be produced by intestinal L. salivarius isolates using the same enzymatic production and export machinery. Such diversity may contribute to their ability to dominate and compete within the complex microbiota of the mammalian gut.
    • Subspecies diversity in bacteriocin production by intestinal Lactobacillus salivarius strains

      O'Shea, Eileen F.; O'Connor, Paula M.; Raftis, Emma J.; O'Toole, Paul W.; STANTON, CATHERINE; Cotter, Paul D.; Ross, R Paul; Hill, Colin; Department of Agriculture, Food and the Marine, Ireland; Science Foundation Ireland; et al. (Landes Bioscience, 2012-10)
      A recent comparative genomic hybridisation study in our laboratory revealed considerable plasticity within the bacteriocin locus of gastrointestinal strains of Lactobacillus salivarius. Most notably these analyses led to the identification of two novel unmodified bacteriocins salivaricin L and salivaricin T produced by the neonatal isolate L. salivarius DPC6488 with immunity, regulatory and export systems analogous to those of abp118, a two-component bacteriocin produced by the well characterized reference strain L. salivarius UCC118. In this addendum we discuss the intraspecific diversity of our seven bacteriocin-producing L. salivarius isolates on a genome-wide level, and more specifically, with respect to their salivaricin loci.
    • Synthesis of trypsin-resistant variants of the Listeria-active bacteriocin salivaricin P

      O'Shea, Eileen F.; O'Connor, Paula M.; Cotter, Paul D.; Ross, R Paul; Hill, Colin; Department of Agriculture, Food and the Marine, Ireland; Science Foundation Ireland; Teagasc Walsh Fellowship Programme (American Society for Microbiology, 25/06/2010)
      Two-component Salivaricin P-like bacteriocins have demonstrated potential as antimicrobials capable of controlling infections in the gastrointestinal tract (GIT). The anti-Listeria activity of salivaricin P is optimal when the individual peptides, Sln1 and Sln2, are added in succession in a 1:1 ratio. However, as degradation by digestive proteases may compromise the functionality of these peptides within the GIT we investigated the potential to create salivaricin variants with enhanced resistance to the intestinal protease, trypsin. A total of 11 variants of the salivaricin P components were generated in which conservative modifications at the trypsin-specific cleavage sites were explored in order to protect the peptides from trypsin degradation while maintaining their potent antimicrobial activity. Analysis of these variants revealed that eight were resistant to trypsin digestion while retaining antimicrobial activity. Combining the complementary trypsin resistant variants Sln1-5 and Sln2-3 resulted in a MIC50 of 300 nM against Listeria monocytogenes, a 3.75-fold reduction in activity compared to wild-type salivaricin P. This study demonstrates the potential of engineering bacteriocins variants which are resistant to specific protease action but which retain significant antimicrobial activity.