Use of the rotating wall vessel technology to study the effect of shear stress on growth behaviour of Pseudomonas aeruginosa PA01

In the lung mucus of cystic fibrosis (CF) patients, P. aeruginosa forms matrix-enclosed microcolonies which cause chronic infections representing the major cause of mortality in CF-patients. The lung mucus of CF-patients is probably characterized by low fluid-shear as the main shear-causing factor, i.e. mucociliary clearance, is absent. In this study, the influence of fluid-shear on the growth behavior of P. aeruginosa PA01 was investigated using a low-shear suspension culture device, the RWV. Cultivation in low-shear induced a self-aggregating phenotype of P. aeruginosa PA01, resulting intheformationofbiofilms in suspension similar to what has been described in CF-mucus. The addition of a ceramic bead to the culture medium in the RWV created a higher-shear condition which led to the formation of surface-attached rather than suspensionbiofilms. In low-shear cultureconditions, a significant increase of the rhl N-butanoyl-L-homoserine lactone directed quorum sensing (QS) system and the psl-polysaccharide synthetic locus was demonstrated using gene expression analysis. Accordingly, the low-shear condition induced a higher production of rhamnolipids, which is controlled by the C4-HSL QS-system and is known toplay a role in CF-lungpathology. These results indicate that fluid-shear has an impact on the growth phenotype of P. aeruginosa which might play a role in CF-lung infections caused bythis bacterium.