| Protein glycosylation has been shown to have important roles in metabolism, cell recognition, cell migration, development, and immunity. Glycosylation is often required for bacterial adhesion to a host which occurs during initial events of pathogen recognition and adhesion of glycoconjugates. Thorough understanding of these interactions is essential to the development of strategies to target bacterial adhesion events.;The nematode Caenorhabditis elegans provides an excellent model to study carbohydrate dependent host-pathogen interactions. In Caenorhabditis elegans (C. elegans), the coryneform Microbacterium nematophilum) causes an infection of the cuticle, leading to an innate immune response characterized by a distinct swelling in the anal region of the cuticle and surrounding tissues. Little is known about adhesins in these bacteria and this work represents the first detailed analysis of the basis for M. nematophilum adhesion to host tissue.;In a genetic screen of C. elegans for altered susceptibility to M. nematophilum infection, almost all of over twenty bacterially unswollen or bus mutants were resistant to M. nematophilum infection. The bus mutants studied here were chosen as a model of carbohydrate pathogen interactions because BUS-2 and BUS-4 are predicted core-I galactosyltransferases and previous work with other mutants also resistant to M. nematophilum had shown that they contain altered core-I type oligosaccharides.;When glycans from the C. elegans bus-2 and bus-4 mutants were compared to those of the wild-type, a reduction in the percent total ion abundance of core-1 like O-glycans was found upon examination of the mass spectra obtained for the pools of beta-eliminated and permethylated glycans. As they have lower abundances in the resistant strains bus-2 and bus-4, it seems likely the core-1 glycans serve as ligands for M. nematophilum adhesion in wild-type C. elegans.;When compared to those of the wild type, the bus-2 glycosylation profiles revealed an increase in the abundance of a new class of C. elegans O-glycans. In the bus mutants, these glycans were found to be increased in abundance in the region where infection was observed on wild-type C. elegans, the posterior intestine, where red fluorescent protein rescue experiments also demonstrated normal BUS-2 expression. The novel glycans are high in molecular weight, highly fucosylated, and feature a unique HexA-containing core structure that was previously unreported in C. elegans. They may serve as barriers to M. nematophilum adhesion and their structures may suggest features that would be useful in candidates for pharmacological intervention to prevent infection. |
