Identification of a gene, pilF, required for type 4 fimbrial biogenesis and twitching motility in Pseudomonas aeruginosa.

Many bacterial pathogens produce a class of surface structures called type 4 fimbriae. In Pseudomonas aeruginosa these fimbriae are responsible for adhesion and translocation across host epithelial surfaces. We have identified a novel gene involved in the complex process of type 4 fimbrial biogenesis. This gene, termed pilF, is located on SpeI fragment S at 30 min on the P. aeruginosa genomic map, which is the sixth region on the chromosome shown to contain a fimbrial-associated gene. The PilF protein has a predicted M(r) of 22402, and together with a highly homologous upstream ORF shares a chromosomal arrangement similar to that found in Haemophilus influenzae. A pilF mutant is blocked in the export/assembly of the fimbrial subunit PilA, and accumulates this protein in the membrane fraction. Complementation studies indicate that the cloned pilF gene is able to restore the expression of surface fimbriae, twitching motility and susceptibility to fimbrial-specific bacteriophage.