The Core‐1 O‐glycans of Microbacterium nematophilum Resistant Caenorhabditis elegans bus‐4 mutants are altered

Microbacterium nematophilum causes a cutaneous infection of the Caenorhabditis elegans hind gut initiated by adhesion to the rectum, anus and surrounding tissues. The C. elegans bus mutants are altered in their susceptibility to this infection and many of these mutants harbor a lesion in a genetic component required for glycoconjugate synthesis. The bus‐4 gene encodes a core‐1 glycosyltransferase homolog predicted to act in the synthesis of O‐glycans. Strains that are deficient in this gene are resistant to M. nematophilum infection. This situation suggests that M. nematophilum requires the presence of host O‐glycans in order to infect. Using mass spectrometry based techniques we show that indeed the bus‐4 mutants are deficient in core‐1 O‐glycans. Neutral core‐1 O‐glycans were diminished while acidic ones were increased in abundance. High performance mass spectrometry revealed that isoform distributions were altered suggesting that a core modifying glycosyltransferase is deficient leading to the observed shift in neutral and acidic O‐glycan pools. Lectin analysis of delipidated fixed bus‐4 nematodes with Agaricus bisporus (ABA) lectin, specific for the conserved Galβ1,3GalNAc‐ present in all core‐1 O‐glycans, revealed that the core‐1 O‐glycans were diminished over the surface of the cuticle including the region normally infected. These findings strongly suggest that host core‐1 O‐glycans are required for M. nematophilum infection. The bus‐4 mutants are also resistant to infection by Yersinia pestis and Yersinia pseudotuberculosis. Therefore, these glycans may be required for infection by these Yersinia spp as well.