Bacterial Glycome as Antibacterial Targets  (2011 - Present)

Investigator:  Christopher Reid, Bryant University
Co-Investigator:  Kirsten Hokeness, Bryant University
Collaborative Mentor: Amit Basu, Brown University

Abstract:  The manifestation of multidrug resistance in bacteria over the past several decades has resulted in one of the foremost challenges in the management of infectious diseases. The question is, how do we address this growing problem? One solution to stem the growing rise in antimicrobial resistance is to investigate new targets, while another approach is to re-examine classical antibacterial targets with a fresh perspective. The bacterial glycome provides the potential for a wealth of untapped targets for antimicrobial discovery. Bacteria produce a wide array of polysaccharides and glycoconjugates including peptidoglycan (PG) and lipoteichoic acids (LTA). Given the vast diversity of glycoconjugates in bacteria, this project will focus on two; PG and LTA. First, PG, heteropolymer of N-acetylglucosamine (GlcNAc) and N-acetylmuramic acid (MurNAc) and adjacent strands are cross-linked via peptide-cross bridges linked to MurNAc. Unlike the highly variable stem-peptides, the polysaccharide backbone is constant across all bacterial species that produce PG. This makes the enzymes that act on the polysaccharide an attractive target for antibacterial development. The first aim of this project will focus on two classes of PG degrading enzymes, lytic transglycosylases (LTs) and N-acetylglucosaminidases (GlcNAcase). We hypothesize that LTs and GlcNAcases pose an attractive target for the development of lead compounds due to their roles in cell growth and division. A library of triazole based glycoconjugates will be investigated as potential inhibitors of these enzymes. This work will involve the biochemical characterization of two enzymes from Clostridium difficile, the LT CD0551, and the GlcNAcase CD1034. The second aim of this proposal will look at LTA from C. difficile and its role in hostpathogen interaction. The LTA structure of C. difficile is unique among the Phyllum Firmicutes and appears to lack D-alanine, a key contributor to immunogenicity in other pathogens. Here we propose to investigate the role of C. difficile LTA in the infection process. We will investigate the role LTA plays in stimulating the immune system utilizing both purified LTA and C. difficile strains in which genes involved in LTA biosynthesis have been inactivated via insertional mutagenesis in tissue culture based assays.