Glycan chain length. The box and whiskers diagram illustrates variations in the percentage of free reducing termini in the peptidoglycan, which are a measure of the glycan chain length. Lower values such as obtained with the femAB null mutant AS145 and its femAB+ derivative BB1305 indicate an elongated glycan chain. The square marks the median of six measurements, the lower and upper border of the box is given by the first and the third quartile, respectively. The minimum and maximum values obtained are shown by horizontal bars.