Use of the Rotating Wall Vessel (RWV) technology to study the effect of shear stress on growth behavior of Pseudomonas aeruginosa PA01

The biofilm phenotype of Pseudomonas aeruginosa
enables this opportunistic pathogen to develop resistance
to the immune system and antimicrobial agents.
Pseudomonas aeruginosa biofilms are generated
under varying levels of shear stress, depending on the
infection site. 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 behaviour of P. aeruginosa
PA01 was investigated using a low-shear suspension
culture device, the rotating wall vessel (RWV). Cultivation
in low shear induced a self-aggregating phenotype
of P. aeruginosa PA01, resulting in the formation
of biofilms 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 highershear
condition which led to the formation of surfaceattached
rather than suspension biofilms. In low-shear
culture conditions, a significant increase of the rhl
N-butanoyl-L-homoserine lactone (C4-HSL) 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 to play a role in CF lung pathology. 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 by this bacterium.