The host-pathogen interactions in the Caenorhabditis elegans animal model: the role of glycosylation and a tool to screen for probiotic bacteria

In this project, the role of the pmr-1 gene in the glycosylation process and in the host-microrganism interaction was analyzed in C. elegans model system. Glycosylation produces a large number of glycans, polysaccharides whose different morphology reflects the multiplicity of biological processes in which they are involved. The emerging role of glycans in the innate and acquired immunity of vertebrates makes them a target for the study of the molecular mechanisms underlying the host-pathogen interaction, in order to develop new therapeutic approaches. The Ca2+-ATPase, encoded by the pmr-1 gene, appears to be involved in alterations of glycosylation mechanisms, as demonstrated by studies on the homologous PMR-1 protein of Saccharomyces cerevisiae and Kluveromyces lactis. In this work, pmr-1 mutant nematodes, obtained through RNA interference, were exposed to different pathogenic microorganisms, showing an increased survival capacity compared to wild-type individuals, following infection by the Gram-positive Staphylococcus aureus and Enterococcus faecalis pathogens. This increased resistance seems to be related to defects in the oligosaccharide structure of glycoproteins of the cell surface caused by their altered glycosylation. The lack of regular recognition of C. elegans surface glycoproteins by the two pathogens could, in fact, determine the difficult adhesion of bacteria to the nematode and the reduction of their pathogenicity. Furthermore, pmr-1 worms showed a different innate immune and oxidative stress responses, as well as an alteration of the glycocalyx in their gut. Since glycosylation is also involved in beneficial role of host microbiota against pathogens, nematodes were used to preselect probiotic bacteria, whose efficacy will be evaluate after administration on pmr-1 mutants, to measure the response of worms to pathogen infection. Therefore, this study represents a first step in understanding the role of PMR-1 protein in the host-microrganism interaction in C. elegans.