Fig. 3.

Green birefringence, characteristic of amyloid formation, was visualized following staining with CR. (a) Green birefringence of aggregated P1 viewed under cross-polarized light. BSA was used as a negative control. (b) Green birefringence of wild-type S. mutans cells grown on an agar surface compared with similarly grown mutants lacking P1 or sortase transpeptidase. Colonies of a curli-expressing strain of E. coli and its corresponding curli-negative mutant were used as positive and negative controls, respectively. The images were taken using cross-polarized (top panels) and non-polarized (bottom panels) light. Bars, 3 µm (a) and 30 µm (b).