Gale, R. T. | Search bioRxiv

bioRxiv2019

Uncovering the hidden antibiotic potential of Cannabis

The spread of antimicrobial resistance continues to be a priority health concern worldwide, necessitating exploration of alternative therapies. Cannabis sativa has long been known to contain antibacterial cannabinoids, but their potential to address antibiotic resistance has only been superficially investigated. Here, we show that cannabinoids exhibit antibacterial activity against MRSA, inhibit its ability to form biofilms and eradicate pre-formed biofilms and stationary phase cells persistent to antibiotics. We show that the mechanism of action of cannabigerol is through targeting the cytoplasmic membrane of Gram-positive bacteria and demonstrate in vivo efficacy of cannabigerol in a murine systemic infection model caused by MRSA. We also show that cannabinoids are effective against Gram-negative organisms whose outer membrane is permeabilized, where cannabigerol acts on the inner membrane. Finally, we demonstrate that cannabinoids work in combination with polymyxin B against multi-drug resistant Gram-negative pathogens, revealing the broad-spectrum therapeutic potential for cannabinoids.

microbiology↗

bioRxiv2018

Structure and mechanism of TagA, a novel membrane-associated glycosyltransferase that produces wall teichoic acids in pathogenic bacteria

Staphylococcus aureus and other bacterial pathogens affix wall teichoic acids (WTAs) to their surface. These highly abundant anionic glycopolymers have critical functions in bacterial physiology and their susceptibility to {beta}-lactam antibiotics. The membrane-associated TagA glycosyltranserase (GT) catalyzes the first-committed step in WTA biosynthesis and is a founding member of the WecB/TagA/CpsF GT family, more than 6,000 enzymes that synthesize a range of extracellular polysaccharides through a poorly understood mechanism. Crystal structures of TagA from T. italicus in its apo- and UDP-bound states reveal a novel GT fold, and coupled with biochemical and cellular data define the mechanism of catalysis. We propose that enzyme activity is regulated by interactions with the bilayer, which trigger a structural change that facilitates proper active site formation and recognition of the enzymes lipid-linked substrate. These findings inform upon the molecular basis of WecB/TagA/CpsF activity and could guide the development of new anti-microbial drugs.\n\nAUTHOR SUMMARYGram-positive bacteria cause thousands of deaths in the United States each year and are a growing health concern because many bacterial strains have become resistant to commonly used antibiotics. One of the most abundant polymers displayed on the surface of Gram-positive bacteria is wall teichoic acid (WTA), a negatively charged carbohydrate polymer that has critical functions in cell division, morphology, adhesion and pathogenesis. The WTA biosynthetic pathway has drawn significant interest as a drug target because clinically important methicillin-resistant S. aureus (MRSA) strains that lack WTA are defective in host colonization and re-sensitized to {beta}-lactam antibiotics. To understand how bacteria produce WTA, we determined the structure and deduced the enzymatic mechanism of TagA, an important enzyme that is required for WTA synthesis. This research reveals a new method for enzyme regulation, whereby peripheral membrane association enables TagA to adopt its active form as a monomer. As TagA enzymes are highly conserved in bacteria, they can be expected to operate through a similar mechanism. The results of this work provide insight into WTA biosynthesis and could lead to innovative approaches to treat infections caused by pathogenic bacteria.

biochemistry↗