Fig. 3

Comparison of photometer- and plate-reader-based absorbance measurements of CV-stained A. minutissimum biofilms. Biofilms stained with CV were first measured in the wells with a plate reader (left facet). Afterwards CV was extracted with EtOH, transferred into photometric cuvettes and re-measured in a spectrophotometer (right facet). Axenic (ax) and xenic (xen) wells represent the negative and positive controls in this bioassay (non-adherent and adherent cells, respectively; N = 36). Boxes represent the first and third quartiles. Whiskers extend to the lowest and highest value that lies within 1.5-fold of the inter-quartile range (IQR). Black dots are extreme values that lie outside the IQR. Black center lines represent medians. Notches indicated the range of \(1.58 \cdot IQR / \sqrt {N}\) (ca. 95 % confidence interval) around the medians. For a more detailed explanation of box-and-whisker plots and their variants, we recommend reading [40]. See also Additional file 7 for R code and data used to plot this and the following figures