The influence of the surface condition on the adhesion of Pseudomonas fluorescens (ATCC 17552) to copper and aluminium brass

The adhesion of P. fluorescens (ATCC 17552) to copper, zinc and aluminium brass in the absence and presence of a surface oxide layer was evaluated performing comparative batch experiments with various times of exposition. The adhesion of this strain to bare copper and aluminium brass was extremely low even after 120 min of exposition. On aged samples, on the other hand, adhesion increased with time on both metals. The degree of bacterial adhesion to aged metals was found to follow the sequence zinc>aluminium brass>copper, and the differences were related to the composition of the oxide layer. The presence of ZnO in the layer strongly increased the adhesion due to the large co-ordination capacity of Zn2+ ions. Correlation was found between the water contact angle of the metal surface and the degree of bacterial adhesion showing that adhesion increases with the decrease in the contact angle. Bacteria were found to have a hydrophilic surface with a water contact angle of 23.5±2° as determined by the sessile drop method.