Chemical Polyglycosylation and Nanolitre Detection Enables Single-Molecule Recapitulation of Bacterial Sugar Export

Capsular polysaccharides are ubiquitous components of the outermost protective layer of both Gram-positive and Gram-negative bacteria. Unresolved questions remain about the interactions occurring between the capsular polysaccharide and its transporter. Moreover the mechanism of sugar export would not only increase our understanding of this key process, but would also help in the design of novel therapeutics to block capsular polysaccharide export.

Examination of the interactions between the Escherichia coli sugar transporter Wza and very small amounts of fragments of the K30 capsular polysaccharide substrate (resulting from the polyglycosylation based on tetrasaccharide moieties) revealed the translocation of smaller but not larger fragments. The single-molecule recapitulation export was observed throughout at nanolitre detection system that makes use of the bilayer interface between two droplets. Capture events occurring only on the intracellular side of the membrane pore, Wza, were detected, bringing some light on the biosynthetic machinery.