Direct force measurement of bacteria adhesion on metal in aqueous media

The adhesion of bacteria on metal surfaces in aqueous media and the development of biofilm and resultant biofouling are important phenomena in both the natural environment and engineering systems. This work reports on the use of a force microscopy technique to measure bacterial metal adhesion by two anaerobic sulphate-reducing bacteria (Desulfovibrio desulfuricans and a local marine isolate) and an aerobe (Pseudomonas sp.). Using a modified bacteria tip, the atomic force microscope was able to quantify the attraction and repulsion force in the nano-Newton range between the bacteria cell and metal surface in aqueous media. Results show that increasing surface hydrophobicity of the metal, and increasing the ionic strength of the aqueous medium both enhance the adhesion force. The adhesion forces were also influenced by the physiological properties of the bacterium, such as the bacterial surface charges and hydrophobicity.