Bacterial biofilms are aggregates of bacteria engulfed in a matrix that display a strong resistance to external insults. Using commensal Neisseria species,  N. elongata, N. cinerea, and N. mucosa, we tested their ability to form biofilms in the presence of physiologically relevant concentrations of spermidine. Our hypothesis is that spermidine will impair biofilm formation by commensal Neisseria, as it was shown for N. gonorrhoeae. We performed static model biofilm assays on commensal Neisseria species and measured biofilm formation at various concentrations of spermidine (0 mM, 0.5 mM, and 4mM). Our results show that N. elongata increased biofilm formation as spermidine concentration increased. N. mucosa formed a stronger biofilm at 0.5 mM spermidine compared to the other two concentrations. N. cinerea showed minimal biofilm formation compared to the other species, however, it displayed increased biofilm formation at 4 mM spermidine. In conclusion, commensal Neisseria behave differently than N. gonorrhoeae, a closely related species, which displays impaired biofilm formation in the presence of spermidine (4 mM). Next, we will focus on this discrepancy, and identify what genes are involved in biofilm formation for commensal Neisseria, and how they differ from pathogenic Neisseria.
 
