Recognition of Lewis x derivatives present on mucins by flagellar components of Pseudomonas aeruginosa

Pseudomonas aeruginosa binds to human respiratory mucins by mechanisms invo lving flagellar component-receptor interactions. The adhesion of P. aerugin osa strain PAK is mediated by the flagellar cap protein, FliD, without the involvement of flagellin. Two distinct types of FliD proteins have been ide ntified in P. aeruginosa: A type, found in strain PAK, and B type, found in strain PAO1. In the present work, studies performed with the P. aeruginosa B-type strain PAO1 indicate that both the FliD protein and the flagellin o f this strain are involved in the binding to respiratory mucins. Using poly acrylamide-based fluorescent glycoconjugates in a flow cytometry assay, it was previously demonstrated that P. aeruginosa recognizes Le(x) (or Lewis x ) derivatives found at the periphery of human respiratory mucins. The aim o f the present work was therefore to determine whether these carbohydrate ep itopes (or glycotopes) are receptors for FliD proteins and flagellin. The r esults obtained by both flow cytometry and a microplate adhesion assay indi cate that the FliD protein of strain PAO1 is involved in the binding of gly coconjugates bearing Le(x) or sialyl-Le(x) determinants, while the binding of flagellin is restricted to the glycoconjugate bearing Le(x) glycotope. I n contrast, the type A cap protein of P. aeruginosa strain PAK is not invol ved in the binding to glycoconjugates bearing Le(x), sialyl-Le(x), or sulfo sialyl-Le(x) glycotopes. This study demonstrates a clear association betwee n a specific Pseudomonas adhesin and a specific mucin glycotope and demonst rates that fine specificities exist in mucin recognition by P. aeruginosa.