Confocal scanning laser microscopic images of 4-h S. gordonii DL1 biofilm showing simultaneous and equivalent efficiency of labeling of cells with both anti-DL1-QD655 conjugate (15 μg protein/ml with DOL of 3) and anti-DL1-Alexa Fluor 546 conjugate (5 μg protein/ml). Maximum projection image of the QD655 channel (A, blue), Alexa Fluor 546 channel (B, red), and overlay (C, purple [red plus blue]) showing absence of interference of labeling by conjugates. The biofilm was first labeled with anti-DL1-QD655 conjugate and then with anti-DL1-Alexa Fluor 546 conjugate; bar, 4 μm.