L. reuteri biofilms were observed by confocal microscopy. Biofilms were cultured in a flow cell supplied with MRS for 48 hours at 37°C in ambient atmosphere. L. reuteri biofilms (green) were stained with acridine orange and observed by confocal microscopy. A single optical section and the stacked optical sections of ATCC 55730 (A and B, respectively) are shown at 630× magnification. These images are representative of 30 microscopic fields obtained in 3 independent experiments.