FIG. 4.

CV staining (A) and analysis of CR binding assays (B) as a measure of biofilm formation by Y. pestis strains. Y. pestis strains were grown overnight at 26°C for both assays. CV bound to attached bacterial cells was solubilized, and absorbance was measured at 570 nm. For CR binding, equivalent wet cell weights were incubated for 3 h in PMH2 containing 30 μg CR/ml. The amount of CR absorbed by the bacterial cells is expressed in terms of absorbance at 500 nm. CV staining and CR binding values are averages of three or more independent experiments, with error bars indicating standard deviations.