Air-water interface displaces adsorbed bacteria

Video microscopy was employed to observed the spatial distribution of Staphylococcus epidermidis and Pseudomonas aeruginosa adherent to glass and polymer substrates. During rinsing procedures the bacteria remained in their original positions when the surfaces were rinsed with saline for 3 min followed by ethanol for 3 min before exposure to air. When the surfaces were rinsed with saline only, the air-liquid interface disrupted the spatial distribution of the bacteria, removing and redepositing the bacteria in clumps. A moving air-liquid interface of a gas bubble on substrate also displaced bacteria. Such artefacts produced by air-water interfaces should be avoided during bacterial adhesion experiments.