Modulation of gonococcal piliation by regulatable transcription of pilE

The gonococcal pilus, a member of the type TV family of pill, is composed o f numerous monomers of the pilin protein and plays an important role in the initiation of disease by providing the primary attachment of the bacterial cell to human mucosal tissues. Piliation also correlates with efficient DN A transformation. To investigate the relationships between these pilus-rela ted functions, the piliation state, and the availability of pilin, we const ructed a derivative of MS11-C9 (Delta pitE1) in which the lacIOP regulatory sequences control pilE transcription. In this strain, MS11-C9.10, the stea dy-state levels of pilin mRNA and protein directly correlate with the conce ntration of IPTG (isopropyl-beta -D-thiogalactopyranoside) in the growth me dium and can reach near-wild-type levels of expression. Transmission electr on microscopy (TEM) demonstrated that the number of pill per cell correlate d with the steady-state expression levels: at a low level of transcription, single long pill were observed; at a moderate expression level, many singu lar and bundled pill were expressed; and upon full gene expression, increas ed lateral association between pill was observed. Analysis of pilus assembl y by TEM and epithelial cell adherence over a time course of induction demo nstrated that pill were expressed as early as 1 h postinduction. Analysis a t different steady-state levels of transcription demonstrated that DNA tran sformation efficiency and adherence of MS11-C9.10 to transformed and primar y epithetial cells also correlated with the level of piliation, These data show that modulation of the level of pilE transcription, without a change i n pilE sequence, can alter the number of pill expressed per cell, pilus bun dling, DNA transformation competence, and epithelial cell adherence of the gonococcus.