Sugar Coating the Envelope : Glycoconjugates for Microbe-Host Crosstalk

Tremendous progress has been made on mapping the mainly bacterial members of the human intestinal microbiota. Knowledge on what is out there, or rather what is inside, needs to be complemented with insight on how these bacteria interact with their biotic environment. Bacterial glycoconjugates, that is, the collection of all glycan-modified molecules, are ideal modulators of such interactions. Their enormous versatility and diversity results in a species-specific glycan barcode, providing a range of ligands for host interaction. Recent reports on the functional importance of glycosylation of important bacterial ligands in beneficial and pathogenic species underpin this. Glycoconjugates, and glycoproteins in particular, are an underappreciated, potentially crucial, factor in understanding bacteria-host interactions of old friends and foes. Glycoconjugates generate a species-specific barcode on the bacterial cell surface. The extreme diversity of bacterial glycoconjugates renders them ideal ligands to establish specific interactions with the environment.Host cells are covered with lectin receptors designed to discriminate between self and non-self glycoconjugates and signal to the immune system.Most ground has been covered by research on glycoconjugates of species on the pathogenic side of the bacterial spectrum. Glycosylation seems to be closely intertwined with virulence. By the same token, glycosylation can be closely intertwined with symbiotic interactions of beneficial species.Glycosylation of cell surface molecules of (beneficial) bacteria might play a crucial, yet underappreciated, role in microbiota-host interactions and offer unique insights in the understanding of these specific interactions.