Adhesion of Pseudomonas aeruginosa to silicone rubber in a parallel plate flow chamber in the absence and presence of nutrient broth.

Abstract

The physico-chemical cell-surface properties of Pseudomonas aeruginosa AK1 and its adhesion to silicone rubber under flow were compared for cells suspended in phosphate-buffered saline (PBS) or PBS supplemented with 2% nutrient broth. Addition of 2% nutrient broth to cells suspended in PBS yielded minimal growth and did not significantly change the mean zeta potential of the organisms, which was around -13 mV. However, a comparatively larger proportion of the organisms had more negative zeta potentials in the presence of nutrient broth. This change was concurrent with a slight decrease in cell-surface hydrophobicity, as measured by water contact angles, from 119 degrees to around 112 degrees. The initial deposition rate of P. aeruginosa AK1 to silicone rubber, as studied in a parallel plate flow chamber, increased from 344 cm-2 s-1 in the absence of nutrient broth to 505 cm-2 s-1 in its presence. No stationary level of adhesion was observed in the presence of nutrient broth, instead the number of adhering cells increased steadily at a rate of approximately 85 cm-2 s-1. Fluorescent staining of adhering cells demonstrated that for adhesion from buffer only 2% of the adhering cells were metabolically active, whereas in case of deposition from PBS supplemented with nutrient broth, 67% of the adhering cells were metabolically active. It is concluded that the deposition rates measured in the parallel plate flow chamber with 2% nutrient broth added to the PBS suspension represent an interplay of adhesion and surface-associated growth.