Seminal Plasma Promotes Neisseria gonorrhoeae Aggregation and Biofilm Formation.

UNLABELLED: Neisseria gonorrhoeae causes the human-specific disease gonorrhea and is transmitted from person to person primarily via sexual contact. During transmission, N. gonorrhoeae is often exposed to seminal fluid and must adapt to this change in environment. Previous work demonstrated that seminal fluid facilitates N. gonorrhoeae motility and alters epithelial cell interactions. In this study, exposure to seminal fluid was found to decrease surface adherence of gonococci in a manner that was independent of Opa adhesin proteins or type IV pilus retraction. Semen was also shown to cause dispersal of bacteria that had previously established surface adherence. Although surface adherence decreased, interbacterial interactions were increased by seminal plasma both in long-term static culture and on a cell-to-cell basis over shorter time periods. The result of increased bacterium-bacterium interactions resulted in the formation of microcolonies, an important step in the N. gonorrhoeae infectious process. Seminal fluid also facilitated increased bacterial aggregation in the form of shear-resistant three-dimensional biofilms. These results emphasize the importance of the gonococcal response to the influx of seminal fluid within the genital niche. Further characterization of the N. gonorrhoeae response to semen will advance our understanding of the mechanisms behind the establishment of infection in naive hosts and the process of transmission. IMPORTANCE: N. gonorrhoeae is the causative agent of the globally prevalent sexually transmitted infection gonorrhea. An understudied aspect of this human-adapted pathogen is the change in bacterial physiology that occurs during sexual transmission. N. gonorrhoeae encounters semen when transmitted from host to host, and it is known that, when N. gonorrhoeae is exposed to seminal fluid, alterations in bacterial motility and type IV pilus arrangement occur. This work extends our previous observations on this modulation of gonococcal physiology by seminal fluid and demonstrates that seminal plasma decreases surface adherence, promotes interbacterial interactions, and enhances biofilm formation.