Effect of surface shear stress on the attachment of Pseudomonas fluorescens to stainless steel under defined flow conditions

Abstract

The application of the radial-flow growth chamber to the study of the initial stages of bacterial adhesion to surfaces under flowing conditions is reported. The adhesive properties of the bacterium Pseudomonas fluorescens (NCIB 9046) to stainless steel (type AISI 316) were found to be highly dependent on surface shear stress and the time and concentration of cells used in the incubation procedure. Maximum levels of adhesion occurred in zones of lowest surface shear stress, particularly less than 6-8 Nm(-2). Adhesion was still noticeable at shear stresses even up to 130 Nm(-2). Significant detachment of cells from a monolayer attached under static conditions was found to occur at surface shear stresses in excess of 10-12 Nm(-2).

Effects of Substratum Topography on Bacterial Adhesion

“…Discussions with industry have indicated that there is a general perception that rough surfaces colonize more rapidly than smooth surfaces due to more surface area available for attachment and that the greatest initial accumulation is in the bottoms of roughness elements because of protection from shear. This thought has also been proposed in the literature by Duddridge et al (14). Schmidt (30) states that hydrodynamics in the vicinity of roughness elements fosters preferential attachment of yeast cells in valleys of stainless-steel surfaces when the roughness elements are greater than one.…”

“…A wide range of shear stresses was tested and it was noticed that the cells transported to the surface attached reversibly and were washed off again at rates increasing with the surface shear stress. There was a critical surface shear stress of 6 -8 N/m 2 above which the extent of attachment dropped off sharply (14).…”

“…Cells tend to be associated with the chemically heterogeneous weld structures in stainless steel, but the issue is complicated by the presence of stagnant water at the weld crown and roots, particularly where undercut, suck-back, or excessive reinforcement exists (40). It has been hypothesized that cells deposit in milling crevices because they are protected from shear arising from flow (14). A wide range of shear stresses was tested and it was noticed that the cells transported to the surface attached reversibly and were washed off again at rates increasing with the surface shear stress.…”

Simultaneous monitoring of the adsorption and desorption of colloidal particles during deposition in a parallel plate flow chamber

“…[16] in which A l is the area blocked by an adhering particle, usually expressed as a factor 7, according to [9] A1 = 7ra23" [17] with a the particle radius. Due to hydrodynamic interactions and electrostatic repulsions between adhering particles, 3' can become as high as 20-30 (10).…”

“…Thorough understanding of colloidal particle deposition is also important for the proper design of experimental systems to study particle deposition (8) and among the systems used we mention the radial flow chamber (9), the stagnation point flow chamber (10,11 ), the rotating disk system (12), and the parallel plate flow chamber ( 13,14). 1 To whom correspondence should be addressed.…”