Revealing the interfacial dynamics of Escherichia coli growth and biofilm formation with integrated micro- and macro-scale approaches

Bacterial biofilms present significant challenges across microbiology, environmental science, water management, and healthcare. This study employs Quartz crystal microbalance with dissipation monitoring (QCM-D) and interfacial rheology system (IRS) for in situ analysis of Escherichia coli biofilm growth and viscoelastic properties. By monitoring biofilm development at both bulk and micro scales in real-time, we identified three distinct growth phases: surface attachment and initial growth, maturation, and dispersion. Optimal biofilm formation occurred in Luria-Bertani medium medium at 5% (v/v) inoculation, as indicated by high complex viscosity and modulus values of 5.38 mPa·s and high complex modulus of 169.13 kPa. IRS data corroborated these findings, showing consistent elastic and viscous behavior patterns, with the storage modulus ( G ′) reaching 0.057 Pa·m and loss modulus ( G ″) peaking at 0.016 Pa·m during the maturation phase. Our results highlight the sensitivity of QCM-D in measuring biofilm properties and the effectiveness of using combined micro- and macro-scale methods for comprehensive biofilm characterization.