Glycobiology of a novel Tannerella species

The globally occurring gum disease periodontitis critically involves the pathogenic bacterium Tannerella forsythia acting as a late colonizer of a polymicrobial biofilm, commonly known as dental plaque. We found that this bacterium has a unique cell surface protein glycosylation, which underpins its pathogenicity by influencing the relationship with other biofilm bacteria and the host through dedicated glycobiological and glycoimmunological interactions; a specific sugar acid (nonulosonic acid) seems to be pivotal to these interactions. A comparison of all publicly available genome sequences of periodontitis-associated T. forsythia strains revealed the presence of a distinct gene cluster that underlays protein glycosylation. In contrast, the genome of the novel, putative periodontal health-associated Tannerella species BU063, which is the closest phylogenetic relative to T. forsythia, has a different glycosylation gene cluster lacking genes for sugar acid biosynthesis. We hypothesize that an altered glycome contributes to the difference of periodontal pathogenesis by Tannerella sp. BU063 and provides a new foundation to further understand the genome evolution and mechanisms of bacteria-host interaction in closely related oral microbes with different pathogenicity potential. Initial data indicate differences in surface-layer protein glycosylation and immunogenicity of Tannerella sp. BU063 compared to T. forsythia. Our novel procedures for cultivation and genetic manipulation of Tannerella sp. BU063 make detailed glycobiological investigations possible. We will investigate the glycoinfrastructure of the Tannerella sp. BU063 cell envelope and determine possible implications for the bacterium`s biofilm lifestyle and interaction with the host. Methods include anaerobic bacterial cultivation, mass spectrometry (MS) and nuclear magnetic resonance spectroscopy (NMR) for glycan structure elucidation, glycoproteomics, genetic manipulation, immune response profiling, biofilm techniques, and imaging. This project generates glycobiology information on a novel oral Tannerella species and aims at delineating glycobiology-mediated mechanisms that could support the association of this bacterium with periodontal health. In relation to the glycobiology knowledge of the pathogenic relative T. forsythia, this project might provide novel insight into the pathogenesis of periodontitis and pinpoint novel therapeutic and prophylaxis approaches against the disease. It also furthers our knowledge on the Bacteroidetes phylum, to which Tannerella species are affiliated, since this bacterial phylum is prominent not only in the oral but also in the gut microbiome. This project is a collaboration between Christina Schäffer (principal investigator; microbiology, glycobiology, biofilm, imaging), Friedrich Altmann (MS), Markus Blaukopf (NMR), all Universität für Bodenkultur, Vienna, Austria, Oleh Andrukhov (immunology; Medical University, Vienna, Austria), and Georgios N. Belibasakis (interaction studies with selected host cells; Karolinska Institutet, Huddinge, Sweden).