Characterisation of bacterial adhesion and removal in a flow chamber by micromanipulation measurements

Flow device analyses and micromanipulation were used to assess the adhesive and cohesive integrity of the immobilised bacterial populations (biomass) of Pseudomonas fluorescens, which were harvested at different growth times and applied to a substrate made of stainless steel subsequently accommodated in a specially designed flow chamber. After the biomass was exposed to a fluidic environment for a period of time, the biomass samples were removed from the flow chamber and the apparent adhesion and cohesion of the remaining biomass was measured using a micromanipulation technique. The surface area of the substrate covered by the biomass exposed to the fluid flow was monitored by a digital camera and then quantified by image analysis. The results indicate a strong correlation between micromanipulation measurements and flow chamber experiments. The micromanipulation data show that the apparent adhesive strength of the biomass increased with the growth time. Moreover, the apparent adhesive strength was found to be stronger than the bacterial cohesive strength. The data was used to interpret the removal behaviour of the biomass from the flow chamber. Using these techniques, specific mechanisms of biomass detachment from a surface and optimised cleaning strategies can be postulated.