A representative example of a thin section image. (a) A transmitted light image shows a qualitative representation of the biofilm. (b) The fluorescence image, showing the green fluorescent protein (GFP) signal, is used for quantification. (c) The GFP fluorescence image is thresholded to differentiate between biofilm (white) and background (black), forming a binary image. The area of the biofilm signal is quantified and divided by the calculated visible arc length (0.923 mm) to calculate a representative average biofilm thickness.