Termination of Poly- N-acetylglucosamine (PNAG) Polymerization with N-Acetylglucosamine Analogues

Abstract

Bacteria require polysaccharides for structure, survival, and virulence. Despite their central role in microbiology, few tools are available to manipulate their production. In E. coli, the glycosyltransferase complex PgaCD produces poly-N-acetylglucosamine (PNAG), an extracellular matrix polysaccharide required for biofilm formation. We report that C6-substituted (H, F, N₃, SH, NH₂) UDP-GlcNAc substrate analogues are inhibitors of PgaCD. In vitro, the inhibitors cause PNAG chain termination, consistent with the mechanism of PNAG polymerization from the nonreducing terminus. In vivo, expression of the GlcNAc-1-kinase NahK in E. coli provided a non-native GlcNAc salvage pathway that produced the UDP-GlcNAc analogue inhibitors in situ. The 6-fluoro and 6-deoxy derivatives were potent inhibitors of biofilm formation in the transformed strain, providing a tool to manipulate this key exopolysaccharide. Characterization of the UDP-GlcNAc pool and quantification of PNAG generation support PNAG termination as the primary in vivo mechanism of biofilm inhibition by 6-fluoro UDP-GlcNAc.