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 mu m) the fractal dimension of the biofilm was 2.94, close to the topological dimension. At larger scales (12-30 mu m) 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.