Metabolic Glycan Labeling in Bacteria Using Rare Azido L-sugars

The rapid rise of antibiotic resistance demonstrates the ineffectiveness of existing antibiotics. Bacterial glycans are compelling therapeutic targets as they link to pathogenesis and contain rare monosaccharides absent from human cells. However, the systematic study of bacterial glycans remains challenging due to the presence of exclusively bacterial sugars which hamper traditional glycan analyses. Thus, the development of chemical tools to study bacterial glycans is a crucial step toward understanding and altering these biomolecules. This project employs metabolic oligosaccharide engineering to accelerate the investigation of bacterial glycans bearing rare deoxy amino L-sugars. Briefly, azide-containing analogs of N-acetyl L-pneumosamine, N- acetyl-L-quinovosamine, N-acetyl L-rhamnosamine, and N-acetyl L-fucosamine were screened for metabolic incorporation into glycans in a range of pathogenic and symbiotic bacteria. L-sugar analogs were narrowly incorporated into select pathogenic species that reportedly express L-sugar-presenting epitopes, namely Plesiomonas shigelloides and Vibrio vulnificus. Surprisingly, L-sugar analogs were also utilized by the pathogen Campylobacter jejuni despite having no previous reports of L-sugar-containing glycans in this species. In contrast, the gut symbiont Bacteroides fragilis did not exhibit any appreciable utilization of L-sugar analogs. Distinct strains of L-sugar bacteria displayed diverse azide-labeled glycan profiles. Finally, azido sugars selectively labeled glycoproteins in P. shigelloides and V. vulnificus. Further application of metabolic probes based on rare sugars will refine our knowledge of glycans in diverse bacteria and aid the design of novel antibiotics