Pilus-mediated adhesion is essential in the pathogenesis of Neisseria menin
gitidis (MC) and Neisseria gonorrhoeae (GC). Pili are assembled from a prot
ein subunit called pilin. Pilin is a glycoprotein, and pilin antigenic vari
ation has been shown to be responsible for intrastrain variability with res
pect to the degree of adhesion in both MC and GC. In MC, high-adhesion pili
ns are responsible for the formation of bundles of pill which bind bacteria
and cause them to grow as colonies on infected monolayers. In this work, w
e selected MC and GC pilin variants responsible for high and low adhesivene
ss and introduced them into the other species. Our results demonstrated tha
t a given pilin variant expressed an identical phenotype in either GC or MC
with respect to bundling and adhesiveness to epithelial cells. However, th
e production of truncated soluble pilin (S pilin) was consistently more abu
ndant in GC than in MC. In the latter species, the glycosylation of pilin a
t Ser63 was shown to be required for the production of a truncated monomer
of S pilin. In order to determine whether the same was true for GC, we engi
neered various pilin derivatives with an altered Ser63 glycosylation site.
The results of these experiments demonstrated that the production of S pili
n in GC was indeed more abundant when pilin was posttranslationally modifie
d at Ser63. However, nonglycosylated variants remained capable of producing
large amounts of S pilin. These data demonstrated that for GC, unlike for
MC, glycosylation at Ser63 is not required for S-pilin production, suggesti
ng that the mechanisms leading to the production of S pilin in GC and MC ar
e different.