Towards real-time observation of conditioning film and early biofilm formation under laminar flow conditions using a quartz crystal microbalance

Abstract A real-time quartz crystal microbalance (QCM) technique was employed to monitor early formation of Pseudomonas fluorescens biofilms. To better understand the dynamic process of conditioning film and early biofilm formation, all experiments were conducted in a laminar flow-through chamber under various environmental conditions. Prior to early biofilm formation, a conditioning film comprising organic, inorganic and macromolecular substances was detected over the sensor chip surface within an extremely short duration due to their instantaneous adsorption. Based on atomic force microscopy (AFM) observations, we identified different surface features associated with various conditioning films, demonstrating that the sensor chip surface displayed complex properties in terms of surface topography, roughness, water contact angle, and conditioning film chemistry. There appeared to be a lag time before early biofilm formation. The rate of early biofilm formation was found to differ considerably, depending upon the characteristics of conditioning films and environmental conditions. However, subsequent biofilm formation could be mediated by environmental conditions, reflecting the complex and dynamic process of biofilm development. Of particular interest was the direct in situ real-time observation of the overall sequence of biofilm development processes using a QCM, starting with conditioning film formation, followed by initial bacterial adhesion and subsequently by biofilm formation.