Summary: Positive cooperativity is a mechanism proposed to account for the adhesion of bacteria to surfaces. In this paper, two methods that both claim to assess experimentally cooperative phenomena, viz. Scatchard analysis of adhesion data (using adhesion to vials) and analysis of the spatial arrangement of adhering cells (using a flow chamber), were compared and critically evaluated. Three oral strains were used and the substrata involved were glass (hydrophilic) and silicone-coated glass (hydrophobic) employed with or without a salivary coating. Scatchard analysis and near-neighbour analysis of adhering cells yield similar conclusions with regard to the mechanism of adhesion of the cells, provided that adhering cells are sufficiently immobilized under the experimental conditions. In the case of incomplete immobilization, near-neighbour collection results from sliding of adhering cells rather than from cooperative phenomena. Also, the agreement between the conclusions from both methods seems to be better, the more reversibly the cells adhere. Positive cooperativity can be absent or present on saliva-coated substrata with a distinct effect of the substratum hydrophobicity, despite the presence of an adsorbed film. This suggests that a different pellicle develops on a hydrophobic substratum than on a hydrophilic substratum. This is confirmed by our observation that the amino acid composition of salivary films in different on both types of substratum.


Article metrics loading...

Loading full text...

Full text loading...

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error