Fig. 2

Biofilm formation of N16961 phase variants. a Following 48 h of static incubation at 30 °C, liquid cultures were poured off and the remaining attached biofilm material was stained with 0.1% crystal violet and quantified by measuring the absorbance at 570 nm. Represented in the graph are the average absorbance values of 12 replicates of N16961, 18 replicates (6 per individual variant) of N16961R, 18 replicates (6 per individual variant) of N16961SD, and 6 replicates of the uninoculated control. Error bars show standard deviations. Samples indicated with the same letter were not significantly different according to Tukey’s post-test (P < 0.05). b Following 48 h of static incubation at 30 °C, liquid cultures were carefully poured out and the pellicles that had formed at the air-broth interface during incubation were retained and repositioned at the side of each glass tube to be photographed