FIG 2.
Spectra of overnight bacterial cultures with CR dye. Curli-producing cultures were PQN4 cells harboring the pBbB8k_csgBACEFG plasmid induced with 100 μM arabinose. Cultures without curli were PQN4 cells without plasmid, and the medium control contained LB only, which was used for all samples. (a) Fluorescence spectra of bacterial cultures grown overnight with 25 μg/ml CR dye (solid lines) or without dye (dashed lines). Excitation spectra (left curves) were found at a fixed emission wavelength (λem) of 625 nm, and emission spectra (right) at a fixed excitation wavelength (λex) of 525 nm. (b) Fluorescence spectrum of the CR in the presence of curli-producing cells, normalized to remove the background signal from cell culture control without dye. (c) Absorbance spectra of the overnight cultures with and without CR. (d) Normalized absorbance spectra for CR-containing cultures, displaying the characteristic shift in CR absorbance with curli binding.