Open AccessIdentification of Two Distinct Types of Flagellar Cap Proteins, FliD, in Pseudomonas aeruginosa
Author(s) -
Shiwani K. Arora,
Nandini Dasgupta,
Stephen Lory,
Reuben Ramphal
Publication year - 2000
Publication title -
infection and immunity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.508
H-Index - 220
eISSN - 1070-6313
pISSN - 0019-9567
DOI - 10.1128/iai.68.3.1474-1479.2000
Subject(s) - flagellin , biology , polyclonal antibodies , pseudomonas aeruginosa , flagellum , epitope , microbiology and biotechnology , serotype , antibody , gene , sequence analysis , bacteria , genetics
Binding ofPseudomonas aeruginosa strain PAK to mucin has been shown to be mediated by the flagellar cap protein, product of thefliD gene. Since the flagellar cap is very likely an exposed structure, the FliD polypeptide should be recognized by the host immune system, analogous to the recognition of dominant epitopes located in the exposed parts of the flagellin polypeptide within the assembled flagellum. InP. aeruginosa , a number of distinct flagellin variants are made, and these variable sequences presumably allow the newly infectedP. aeruginosa to escape recognition by the antibody induced during a previous infection. Since similar mechanisms may direct the selection of FliD variants, we examined the extent of sequence heterogeneity among various FliD sequences among a selected group ofP. aeruginosa . The results of PCR and nucleotide sequencing of thefliD region of eight differentP. aeruginosa strains (laboratory strains PAK, PAO1, and PA103; clinical strains 1244, CS2, and CS32; cystic fibrosis strains CS29 and MDR) suggested that there were two distinct types of FliD inP. aeruginosa , which we named A type and B type. The results of Western blotting using the polyclonal antibodies raised against the purified FliD of A type (PAK) or B type (PAO1) further confirmed the existence of two distinct antigenic types of FliD proteins, with no cross-reactivity between the two serotypes. Further Western immunoblot analysis of the same strains using polyclonal FliC antibody showed that the strains with A-type FliD possessed a-type FliC and those with B-type FliD had b-type FliC. Similar Western blot analyses of 50 moreP. aeruginosa strains obtained from varied sources revealed that all strains contained either A-type or B-type FliD, suggesting the existence of only two types of FliD inP. aeruginosa and indicating thatfliC andfliD were coinherited. This limited diversity of FliC and FliD serotypes seems to be a unique feature of flagellar proteins. A chromosomal mutant having an insertion in thefliD gene ofP. aeruginosa PAO1 was constructed. The motility defect of this mutant and a previously constructed PAKfliD mutant was better complemented with thefliD gene of the homologous types.