CHARACTERIZATION OF A PSEUDOMONAS-AERUGINOSA GENE-CLUSTER INVOLVED INPILUS BIOSYNTHESIS AND TWITCHING MOTILITY - SEQUENCE SIMILARITY TO THE CHEMOTAXIS PROTEINS OF ENTERICS AND THE GLIDING BACTERIUM MYXOCOCCUS-XANTHUS

The type 4 pill of Pseudomonas aeruginosa are important cell-associate d virulence factors that play a crucial role in mediating (i) bacteria l adherence to, and colonization of, mucosal surfaces, (ii) a novel mo de of flagella-independent surface translocation known as 'twitching m otility', and (iii) the initial stages of the infection process for a number of bacteriophages. A new set of loci involved in pilus biogenes is and twitching motility was identified based on the ability of DNA s equences downstream of the pilG gene to complement the non-piliated (p ill strain, PA06609. Sequence analysis of a 3.2 kb region directly dow nstream of pilG revealed the presence of three genes, which have been designated pilH, pill, and pilJ. The predicted translation product of the pilH gene (13272 Dal, like PilG, exhibits significant amino acid i dentity with the enteric single-domain response regulator CheY. The pu tative Pill protein (19933 Dal is 28% identical to the FrzA protein, a CheW homologue of the gliding bacterium Myxococcus xanthus, and the P ilJ protein (72523Da) is 26% identical to the enteric methyl-accepting chemotaxis protein (MCP) Tsr. Mutants containing insertions in pill a nd pilJ were severely impaired in their ability to produce pill and di d not translocate across solid surfaces. The pilH mutant remained capa ble of pilus production and twitching motility, but displayed an alter ed motility pattern characterized by the presence of many doughnut-sha ped swirls. Each of these pil mutants, however, produced zones that we re at least as large as the parent in flagellar-mediated swarm assays. The sequence similarities between the putative pilG, ii, I and J gene products and several established chemotaxis proteins, therefore, lend strong support to the hypothesis that these proteins are part of a si gnal-transduction network that controls P. aeruginosa pilus biosynthes is and twitching motility.