Effects of cell surface damage on surface properties and adhesion of Pseudomonas aeruginosa

Bacterial cell surfaces play a crucial role in their adhesion to surfaces. In the present study, physico-chemical cell surface properties of Pseudomon as aeruginosa, isolated from a case of contact lens associated keratitis, a re determined for mid-exponential and early stationary phase cells and for cells after exposure to a lens care solution or after mechanical damage by sonication. Exposure to a lens care solution and mechanical cell surface da mage reduced the cell surface hydrophobicity and water contact angles decre ased from 129 degrees to 96 degrees and 83 degrees, respectively. Zeta pote ntials in saline (-9 mV) were hardly affected after mechanical damage, but tri-modal zeta potential distributions, with subpopulation zeta potentials at -11, -28 and -41 mV, were observed after exposure of bacteria to a lens care solution. X-ray photoelectron spectroscopy indicated changes in the am ounts of oxygen-, nitrogen- and phosphorus-rich cell surface components. Mi d-exponential phase cells had more nitrogen-rich cell surface components th an early stationary phase cells, but water contact angles and zeta potentia ls were not very different. In addition, mid-exponential phase cells adhere d better than early stationary phase cells to hydrophobic and hydrophilic s ubstrate in a parallel plate flow chamber. The capacity of P. aeruginosa to adhere was decreased after inflicting cell surface damage. Exposure to a l ens care solution yielded a larger reduction in adhesion capacity than soni cation, likely because sonication left most of the cells in a viable state, in contrast to exposure to a lens care solution. It is argued that for cli nically relevant experiments. it may be preferable to work; with surface da maged cells rather than with gently harvested organisms. (C) 2001 Elsevier Science B.V. All rights reserved.