Measurement of the force necessary for removal of bacterial cells from a quartz plate

Abstract

The force necessary to remove the cells of a bacterium, an isolate (Bacillus sp.) from grassland soil, from a quartz plate was investigated in phosphate buffer solution by using a well-defined liquid flow caused by electroosmosis. The cells were not removed at a specific strength of removal force but removed over a wide range of force, about 10-14-10-12 N per cell. An exponential relation was observed between the removal force and the number of removed cells in media of pH 7.0,8.0 and 9.0; more cells were removed by a smaller force. Experiments in media of different pH values in the range 3-0 to 9.0 showed that greater force was necessary to remove the cells in media of lower pH. The smaller electrostatic repulsion between the bacterial cells and the quartz plate at lower pH values was considered to result in the greater force needed for removal. The relation between the strength of the removal force and the strength of the adhesion force of the bacterial cells was considered. The findings showed that the cell adhesion was reversible and that the adhesion site was located near the end of the cell.

The cell surface charge of fast- and slow-growing bacteria isolated from grassland soil.

“…A small amount of bacterial suspension (25-50 j l) in 10 mM NaCI was added to 10 mM PBS (5-10 ml) to a concentration of 10' cells/ml. The EPM Charge of Soil Bacteria 67 of the isolates was determined at the upper stationary level of a flat rectangular quartz cell (Rank Brothers, UK) submerged in a water bath (25°C) as previously reported (11). To estimate the reproducibility of the experiments, the measurement of EPM was repeated for two cultures of the same isolate: 12 strains were examined at different pHs; the mean of standard errors of these measurements was 0.19 x 10-8 m2 V -1 s -1.…”

Estimation of the adhesive force distribution for the flagellar adhesion of Escherichia coli on a glass surface

“…The D 99.9 value represents the point at which 0.1% of the microbial cells remained on the substratum. Morisaki [50] measured the force necessary to remove the cells of Bacillus sp. from a quartz plate in phosphate buffer using a liquid flow caused by electroosmosis, and demonstrated that the cells were not removed at a specific strength of removal force but removed over a wide range of force.…”

Microbial Adhesion in Flow Displacement Systems

“…However, when fluid flow exceeds a critical limit (49), resulting wall shear rates may become high enough to prevent adhesion (65,78) or even stimulate detachment. For instance, in aqueous suspensions, wall shear rates of 6,000 to 8,000 s Ϫ1 (equivalent to shear forces of between 6 ϫ 10 Ϫ3 and 8 ϫ 10 Ϫ3 nN) were sufficient to prevent adhesion of Pseudomonas fluorescens to stainless steel, while wall shear rates of 12,000 s Ϫ1 (or shear forces of 12 ϫ 10 Ϫ3 nN) could detach adhering organisms (78).…”