LATERAL AND PERPENDICULAR INTERACTION FORCES INVOLVED IN MOBILE AND IMMOBILE ADHESION OF MICROORGANISM ON MODEL SOLID-SURFACES

Gliding and near-surface swimming of microorganisms are described as a mobile form of microbial adhesion that need not necessarily be revers ible. It is argued that the reversibility of microbial adhesion depend s on the depth of the secondary interaction minimum, calculated from t he forces between an organism and a substratum acting in a direction p erpendicular to the substratum surface. The mobility of adhering micro organism depends on lateral interactions between the organisms. On ide ally homogeneous and smooth model surfaces, only mobile adhesion occur s because the multibody, lateral interactions are weak compared with t he thermal or Brownian motion energy of the organisms. Minor chemical or structural heterogeneities, which exist on all real-life surfaces, yield a lateral interaction on adhering microorganisms. This causes th eir immobilization, which helps to explain the physicochemical nature of microbial gliding or near-surface swimming. Moreover, these lateral interaction energies are one order of magnitude smaller than the Lifs hitz-Van der Waals, electrostatic, and acid-base forces acting perpend icular to substratum surfaces that are responsible for adhesion.