ISOLATION OF A PUTATIVE FIMBRIAL ADHESIN FROM BORDETELLA-PERTUSSIS AND THE IDENTIFICATION OF ITS GENE

We report the purification of a minor Bordetella pertussis fimbrial su bunit, designated FimD, and the identification of its gene (fimD). Fim D could be purified from the bulk of major fimbrial subunits by exploi ting the fact that major, subunit-subunit interactions are more stable in the presence of SDS than minor-major subunit interactions. To loca te the gene for FimD, internal peptides of FimD were generated, purifi ed and sequenced. Subsequently, an oligonucleotide probe, based on the primary sequence of one peptide, was used to clone find. The primary structure of FimD, derived from the DNA sequence of its gene, showed h omology with a number of fimbrial adhesins. Most pronounced homology w as observed with MrkD, a fimbrial adhesin derived from Klebsiella pneu moniae. These observations suggest that FimD may represent a B. pertus sis fimbrial adhesin. With a fimD-specific probe we detected the prese nce of a fimD homologue in Bordetella parapertussis and Bordetella bro nchiseptica but not in Bordetella avium. Cloning and sequencing reveal ed that the B. parapertussis and B. bronchiseptica find product differ ed from the B. pertussis find product in 20 and 1 amino acid residues, respectively. Since B. bronchiseptica is normally not a human pathoge n, but causes respiratory disease in a wide range of non-human mammali an species, this may suggest that FimD recognizes a receptor that is w ell conserved in mammalian species. An in-frame deletion in fimD compl etely abolished FimD expression and also affected the expression of th e major subunits Fim2 and Fim3 suggesting that, in contrast to other a dhesins that are minor components of fimbriae, FimD is required for fo rmation of the fimbrial structure.