IDENTIFICATION OF FIMBRIAL ASSEMBLY GENES FROM DICHELOBACTER-NODOSUS - EVIDENCE THAT FIMP ENCODES THE TYPE-IV PREPILIN PEPTIDASE

Dichelobacter nodosus (Dn) is the causative agent of footrot, an econo mically significant disease of sheep. One of the factors believed to b e involved in the virulence of this organism is its ability to produce type-IV fimbriae, which are the major protective antigens. To investi gate the process of fimbrial biogenesis in Dn, gene probes were constr ucted from pilus biogenesis genes of Pseudomomas aeruginosa (Pa) and u sed to isolate homologues from Dn. A homologue, designated fimP, of th e Pa prepilin peptidase-encoding gene, piID, was cloned using this app roach. The fimP gene product was shown to possess endopeptidase activi ty when produced in Escherichia coli. Two other fimbrial biogenesis ge nes fimN and fimO, whose products show similarity to the Pa PilB and P ilC proteins, respectively, were identified because of their linkage t o fimP. The arrangement of fimN, fimO and fimP in Dn closely resembles the arrangement of pilB, pilC and pilD in Pa.