• Controlled functional expression of the bacteriocins pediocin PA-1 and bactofencin A in Escherichia coli

      Mesa-Pereira, Beatriz; O’Connor, Paula M.; Rea, Mary; Cotter, Paul D.; Hill, Colin; Ross, R Paul; Science Foundation Ireland; SFI/12/RC/2273 (Nature Publishing Group, 2017-06-08)
      The bacteriocins bactofencin A (class IId) and pediocin PA-1 (class IIa) are encoded by operons with a similarly clustered gene organization including a structural peptide, an immunity protein, an ABC transporter and accessory bacteriocin transporter protein. Cloning of these operons in E. coli TunerTM (DE3) on a pETcoco-2 derived vector resulted in successful secretion of both bacteriocins. A corresponding approach, involving the construction of vectors containing different combinations of these genes, revealed that the structural and the transporter genes alone are sufficient to permit heterologous production and secretion in this host. Even though the accessory protein, usually associated with optimal disulfide bond formation, was not required for bacteriocin synthesis, its presence did result in greater pediocin PA-1 production. The simplicity of the system and the fact that the associated bacteriocins could be recovered from the extracellular medium provides an opportunity to facilitate protein engineering and the overproduction of biologically-active bacteriocins at industrial scale. Additionally, this system could enable the characterization of new bacteriocin operons where genetic tools are not available for the native producers.
    • The gut microbiota and the liver. Pathophysiological and clinical implications

      Quigley, Eamonn M.M.; STANTON, CATHERINE; Murphy, Eileen F. (Elsevier BV, 2012-11-06)
      The term microbiota is used to describe the complete population of microorganisms that populate a certain location, such as the gut, and is preferred to the term flora as the former incorporates not just bacteria but also archaea, viruses, and other microorganisms, such as protozoa. Though the potential role of the microbiota (through such concepts as ‘‘the putrefactive principle associated with faeces’’ and ‘‘intestinal toxins’’) in the pathogenesis of systemic disorders has been recognized since antiquity, a firm scientific basis for a role for the gut microbiome in liver disease did not emerge until the middle of the last century with the recognition of the relationship between hepatic coma and the absorption of nitrogenous substances from the intestine [1]. This was followed by the description of abundant coliforms in the small intestine of cirrhotics [2] and the role of bacteria was clinched by trials demonstrating that antibiotics led to clinical improvement in hepatic encephalopathy (HE) [3]. Subsequently, these same gut-derived bacteria were implicated in another complication of chronic liver disease and portal hypertension, spontaneous bacterial peritonitis. Most recently, more credence has been given to a suggestion that has lingered in the background for decades, namely, that the gut microbiota might play a role in the pathogenesis or progression of certain liver diseases, including alcoholic liver disease [4], non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steato-hepatitis (NASH) [5], total parenteral nutrition (TPN)/intestinal failure-related liver disease (IFALD) [6], and primary sclerosing cholangitis (PSC) [7], either through the direct effects of bacteria or their products, via inflammatory mediators such as tumor necrosis factor a (TNF), whose release had been triggered by constituents of the microbiota, or, as in the case of primary sclerosing cholangitis (PSC), through cross-reactivity between microbial antigens and human tissue components (e.g., atypical anti-nuclear cytoplasmic antibodies (p-ANCA), in PSC, recognize both tubulin beta isoform 5 in human neutrophils, and the bacterial cell division protein FtsZ) [8]. Indeed, inflammatory mediators have also been implicated in the development and maintenance of the hyperdynamic circulation that is a feature of portal hypertension [9], in impairing liver function and contributing to haemostatic failure [10]. It is in these contexts that modulation of the microbiota has emerged as a potential therapeutic strategy in the management of liver disease