Racing to build a wall: glycoconjugate assembly in Gram-positive and Gram-negative bacteria.

The last two years have seen major advances in understanding the structural basis of bacterial cell envelope glycoconjugate biosynthesis, including capsules, lipopolysaccharide, teichoic acid, cellulose, and peptidoglycan. The recent crystal and cryo-electron microscopy structures of proteins involved in the initial glycosyltransferase steps in the cytoplasm, the transport of large and small lipid-linked glycoconjugates across the inner membrane, the polymerization of glycans in the periplasm, and the export of molecules from the cell have shed light on the mechanisms by which cell envelope glycoconjugates are made. We discuss these recent advances and highlight remaining unanswered questions.