Figure 4

SYTO9 staining analyzed with confocal microscopy. Different live/dead proportions of S. aureus (right) and P. aeruginosa (left) cells were stained with SYTO9 and examined with CLSM. The live/dead ratios of 10:90 and 90:10 are shown for illustration and comparison. For P. aeruginosa, a small proportion of approximately 10% of the total stained cells exhibits weaker (in 10:90 ratio) or stronger (in 90:10 ratio) fluorescence compared with the rest of the cells. The cells having weaker or stronger fluorescence are indicated by arrowheads. For S. aureus no difference in SYTO9 signal intensity can be observed for live and dead cells.