Anisotropic morphology and fractal dimensions of biofilms

Heterotrophic aerobic biofilm was examined using a confocal laser scanning microscope. The morphology of biofilm cross-sections was characterized by fractal dimension which was calculated from the slope of the pixel-to-pixel correlation function. Two scales were identified with this approach. At a smaller scale (less than 3 μm) the fractal dimension of the biofilm was 2.94, close to the topological dimension. At larger scales (12–30 μm) fractal dimension was considerably smaller (2.50–2.67). At these larger scales the values of fractal dimension were higher when measured in the direction parallel to the flow than those measured perpendicularly to the flow.