Are there critical biofilm phenomena that diffusion does not explain?
This article began with the statement that much of what makes life in a biofilm special can be explained by accounting for diffusive phenomena. Diffusion limitation probably does not explain everything though. It is likely that microorganisms have sensing pathways, which trigger gene expression during biofilm development, and that are independent of diffusion-based concentration gradients. As an approach to this issue, consider the image of an antimicrobial-treated biofilm in Figure 4-9. This specimen shows surviving bacteria (green) in the core of mushroom-shaped clusters that sit above a thin base film of killed (red) cells. Why are the survivors concentrated in the interior of cell clusters?
