• First evidence of production of the lantibiotic nisin P

      Garcia-Gutierrez, Enriqueta; O’Connor, Paula M.; Saalbach, Gerhard; Walsh, Calum J.; Hegarty, James W.; Guinane, Caitriona M.; Mayer, Melinda J.; Narbad, Arjan; Cotter, Paul D.; Teagasc Walsh Scholarship Programme; et al. (Springer Nature, 2020-02-28)
      Nisin P is a natural nisin variant, the genetic determinants for which were previously identified in the genomes of two Streptococcus species, albeit with no confirmed evidence of production. Here we describe Streptococcus agalactiae DPC7040, a human faecal isolate, which exhibits antimicrobial activity against a panel of gut and food isolates by virtue of producing nisin P. Nisin P was purified, and its predicted structure was confirmed by nanoLC-MS/MS, with both the fully modified peptide and a variant without rings B and E being identified. Additionally, we compared its spectrum of inhibition and minimum inhibitory concentration (MIC) with that of nisin A and its antimicrobial effect in a faecal fermentation in comparison with nisin A and H. We found that its antimicrobial activity was less potent than nisin A and H, and we propose a link between this reduced activity and the peptide structure.
    • Gut microbiota as a source of novel antimicrobials

      Garcia-Gutierrez, Enriqueta; Mayer, Melinda J.; Cotter, Paul D.; Narbad, Arjan; Teagasc; Science Foundation Ireland; Biotechnology and Biological Sciences Research Council; 2015066; SFI/12/RC/2273; SFI/11/PI/1137; et al. (Taylor & Francis, 2019-05-22)
      Bacteria, Archaea, Eukarya and viruses coexist in the human gut, and this coexistence is functionally balanced by symbiotic or antagonistic relationships. Antagonism is often characterized by the production of antimicrobials against other organisms occupying the same environmental niche. Indeed, close co-evolution in the gut has led to the development of specialized antimicrobials, which is attracting increased attention as these may serve as novel alternatives to antibiotics and thereby help to address the global problem of antimicrobial resistance. The gastrointestinal (GI) tract is especially suitable for finding novel antimicrobials due to the vast array of microbes that inhabit it, and a considerable number of antimicrobial producers of both wide and narrow spectrum have been described. In this review, we summarize some of the antimicrobial compounds that are produced by bacteria isolated from the gut environment, with a special focus on bacteriocins. We also evaluate the potential therapeutic application of these compounds to maintain homeostasis in the gut and the biocontrol of pathogenic bacteria.