Fluctuations in biofilm topographies: characterization and dynamics*

During biofilm development, colonies grow from sub-micron heights to heights of hundreds of microns. Using white-light interferometry, we measure the biofilm topography of a diverse cohort of microbes with nanometer resolution in the vertical direction, across colonies that span multiple millimeters in radius. We characterize the fluctuations through scale-free metrics like the Hurst exponent and fractal dimension, as well as standard ISO metrics. We explore the emergence of self-similarity in the profiles, as well as low amplitude and high wavelength modes close to their steady state. We then reconcile our experimental observations with well established analytical models and recent bacterial colonies representations.