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Title: The measurement of microbial adhesion
Author: McKay, A. J.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1981
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Microbial adhesion to surfaces is seen as a widespread phenomenon of ecological, economic, and scientific importance. Its quantification in absolute terms is necessary for the study and control of adhesion, but measurement methods must be evaluated in the light of adhesion mechanisms. Two stages of adhesion are recognised, physico-chemical adsorption being followed by biological adhesion stabilisation. This appears to apply to all cell types, and can best be quantified by a dynamic assessment method. The proposed method utilises a continuous range of fluid shear forces across the test surface, adhesion being quantified as the maximum shear against which microbial filming occurs. The Radial Flow Growth Chamber is designed to provide this, culture flowing radially outwards between two parallel discs so that surface shear stress decreases with increasing radial distance from the centre. The system flow analysis is presented in its simplest form, and illustrated graphically. A gram-positive coccoid soil bacterium was used in adhesion tests, using discs of Pyrex and plate-glass, stainless-steel and aluminium. Adhesion could be ranked in the order Steel > Pyrex > Plate-glass and Aluminium. Adhesion to Pyrex and steel was maximal at pH 7.0, declining symmetrically either side of this. The effects of surface properties and pH on adhesion are discussed. Absolute shear values could not be determined from these tests since turbulence at the inlet prevented application of the theoretical analysis. Shaping the inlet to follow the natural streamlines prevented this effect and allowed absolute quantification. The maximum shear stress for adhesion to Pyrex and steel, at pH 6.6, was 22.0 and 23.4 dyne/cm, respectively. The Radial Flow Growth Chamber offers an absolute, meaningful quantification of microbial adhesion. Its use should allow much further investigation of the important attached mode of microbial growth.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available