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

Abstract

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.

Analysis of the contribution of sedimentation to bacterial mass transport in a parallel plate flow chamber

“…The diffusive mass transport rate, j D (z), within the diffusion boundary layer was calculated from j D (z) = −D ∞ ∂c(z) ∂z (8) in which the gradient in bacterial concentration was calculated from the experimentally determined concentration profile at the position z. The theoretical thickness of the diffusion boundary layer, neglecting sedimentation and interaction forces, was calculated according to the following equation [19]: (9) in which ı d is the thickness of the boundary layer for diffusion, Á the dynamic viscosity of fluid, f the mass density of fluid. The values of the parameters adopted for the mass transport indicators in the present study are listed in Table 1.…”

“…Biofilms can be found nearly everywhere, such as in groundwater, pipelines in waterworks, wastewater treatment plants, on the surfaces of heat exchanger plates and biomedical devices, and on ship hulls [1][2][3][4][5]. Flow displacement systems are widely used to study bacterial adhesion to surfaces [6][7][8][9][10] as they allow control of hydrodynamic conditions, including shear rates and mass transport.…”

Influence of support material properties on the potential selection of Archaea during initial adhesion of a methanogenic consortium

“…Nowadays, the use of micro-organisms in the field of bioremediation is common (Garett et al, 2008). Anaerobic digestion, the conversion of organic matter into methane and carbon dioxide by a complex anaerobic microbial consortium, is widely applied to the treatment of agri-industrial wastewaters.…”

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“…During biofilm growth a differentiation of the gene expression pattern can be seen compared to planktonic cells. The production of surface appendages involved in bacterial motility is downregulated due to cell immobility in the biofilm matrix while production of EPS and membrane transport proteins such as porins is up-regulated 10 . The up-and down-regulation of genes is mainly dependent on population density and is controlled by a signal molecule driven communication system known as quorum sensing.…”