Specific and non-specific interactions in bacterial adhesion to solid substrata

Based on a literature review, a hypothesis is forwarded on the mechanism of initial bacterial adhesion to solid substrata, which accounts both for the role of specific microscopic surface components as well as for the role of non-specific macroscopic surface properties (surface free energy, zeta potential or hydrophobicity). Three distinct regions in the adhesion process are suggested in which at large and intermediate separation distances adhesion is mediated by the macroscopic surface properties as surface free energy and surface charge, respectively. At small separation distances specific short-range interactions can occur, leading to a strong and irreversible bonding, provided the water film present in between the interaction surfaces can be removed. A major role of hydrophobic groups, supposed to be associated with bacterial surface appendages is suggested to be its dehydrating capacity, enabling the removal of the vicinal water film yielding small areas of direct contact between protruberant parts of the cell surface and the substratum.