Forces involved in adhesion of Bacillus cereus spores to solid surfaces under different environmental conditions

The adhesion of Bacillus cereus spores (NCTC 2599) to hydrophobic and hydrophilic glass surfaces was studied when environmental conditions were varied. The spores were exposed in media of different polarities as well as different pH and ionic concentrations. With increasing ethanol concentrations, the polarity of the medium was decreased and the predominant force of attraction was found to be hydrophobic. The spore surface was uncharged at a pH around 3, at which value the spore was most adhesive to both hydrophobic and hydrophilic glass. This could be attributable to the absence of electrostatic repulsion. An increased ionic concentration of the bulk increased the degree of adhesion especially to the hydrophilic surfaces. This indicates the suppression of a solvation barrier at high ionic concentrations, when the polymers of the spore surface become dehydrated.