The bacterium Pseudomonas
aeruginosa (PA) produces two carbohydrate binding lectins, designated PA lectin-I and lectin-II (PA-IL, PA-IIL). Both lectins are used by the bacterium to adhere to the glycocalyx of mammalian cells. In addition, the lectins immobilize ciliary beat. The kinetics of ciliary beat inhibition by each individual lectin have been analysed; however, their joint action on cilia has not been reported. Here we demonstrate that PA-IL and PA-IIL inhibit ciliary beat in a similar time-dependent manner. If applied simultaneously, ciliary beat inhibition after five hours of incubation was weaker than if each lectin was applied separately. Thus it can be hypothesized that the lectins compete for the same binding site(s) of the glycocalyx. Sugar inhibition experiments demonstrate that D-galactose and L-fucose inhibit both lectins, although clear preferences of D-galactose for PA-IL and of L-fucose for PA-IIL exist. These interactions have to be kept in mind when designing sugar-based therapies.