Microbial Glycoside Hydrolases and Host Cell Signaling

Abstract

Glycans, carbohydrate-based macromolecules, are present on the surfaces of all prokaryotes and eukaryotes cells. They play critical roles in cell-cell interactions, and host glycans also provide both binding sites and nutrition for commensal microbes. Many bacteria use glycoside hydrolases (GHs) on host-generated glycans and dietary glycans for nutrition and to modulate attachment sites and host protein function. The microbiota found in a single human gut sample has greater than 10,000 GH genes, and many of these gene products have specificity for host glycans. In eukaryotes, glycosylation of cell surface receptors is critical for proper localization and function, including receptors for innate immune signalling. The hypothesis of this project is that human-associated microbiota can express and secrete GHs that can alter the functioning of host immune signalling pathways. In this work, I measure GHs enzyme activity, use bacterial cell-free supernatant and purified enzymes to determine if they can modulate host cell signalling pathways, and examine glycans cell surface modifications by fluorescence microscopy using fluorescent-labelled lectins.