Role of gonococcal surface glycoconjugates, their diversity and their role in bacteria-bacteria interaction and bacteria-host interaction
Bhoopalan, Senthil Velan
Stein, Daniel C
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Bacterial interactions with each other and with host cells play a critical role in the pathogenesis of gonorrhea. Bacterial aggregation was observed to be mediated by the interaction between lipooligosaccharide (LOS) and the opacity-associated protein. In this study, I identified a gene encoding a beta-hexosaminidase (NagZ) in Neisseria gonorrhoeae that modulates gonococcal aggregation and biofilm formation. In comparison to the parental strain, a strain with the nagZ gene deleted produced a biofilm with increased mass. Scanning electron microscopy and confocal laser microscopy were able to visualize differences in the biofilms formed by the two strains. Biofilms formed by a strain deficient in nagZ were disrupted by addition of exogenously added purified NagZ. This is the first study to demonstrate that an enzyme thought to be restricted to peptidoglycan recycling is able to moonlight as biofilm modulator. NagZ could play an important role in promoting bacterial escape from a biofilm, along with previously characterized agents such as Nuc thermonuclease. Using strains defective in surface protein glycosylation, I demonstrate that the increase in biofilm formation seen in nagZ mutant is dependent on PglC-mediated surface protein glycosylation. This is the first study demonstrating the role played by surface glycoconjugates in gonococcal biofilm formation. I used bioinformatic analysis to study the diversity of the other major glycoconjugate on gonococcal surface, LOS. I identified significant differences in the LOS core structure between commensals and pathogens within the Neisseriaceae. I generated preliminary data suggesting that N. gonorrhoeae activate inflammasomes in epithelial cells, resulting in production of IL-18. While activation of inflammasomes does not affect production of other cytokines such as IL-8, IL-8 levels were reduced by using MyD88-inhibitors. Gonococcal-induced inflammasome activation in epithelial cells and production of inflammasome-dependent cytokines were further confirmed in human cervix explants.