Phenotypic characteristics of S. mutans after short-term and long-term hyperosmotic stimuli. (A) Representative Scanning Electronic Microscopy images of S. mutans biofilm on glass surfaces. Images shown were taken at 1000 ×, 5000 × and 10000 × magnification. (B) Representative 3D rendering images of S. mutans biofilms without NaCl for 24 h (upper left), versus with 0.4 M NaCl for either 15 min (upper right) or 24 h (lower left). Bacterial cells and EPS are in situ labelled. Green, the bacteria (SYTO 9); red, the EPS (Alexa Fluor 647). At the right of each panel, the two channels are displayed separately, while the merged image is displayed at the left. Lateral (side) views of each biofilm are displayed at the bottom. Quantitative determination of S. mutans biofilms (lower right) confocal image stacks analyzed by the image-processing software COMSTAT. Results were averaged from 3 independent experiments and are presented as mean ± standard deviation. *, P ≤ 0.05.