Scatter plots and bar graph representation of the populations of SYTO 9 and propidium iodide stained <i>P</i>. <i>aeruginosa</i> PAO1 in water.

Strains were inoculated into sterile water at a concentration of 107 CFU/ml and incubated at room temperature. A) Live and dead cell populations were subjected to LIVE/DEAD staining every week and quantitated by flow cytometry. The quadrant labelled S9 refers to the cells that were stained with SYTO 9 only, which are generally considered to be viable. The quadrant labelled S9PI refers to the cells that stained both with SYTO 9 and PI, which are possibly dead or membrane-compromised, dormant cells. The time points are from day 1, week 1, week 2 and week 4 in water. Each panel represents a population of 50,000 cells per experiment. B) The percentage of SYTO 9 (green bars) and SYTO 9/PI (red bars) stained cells is depicted over an 8-week time course. The values shown are the average S9 and S9PI counts recovered from triplicate flow cytometry samples. Significant differences were determined using one-way ANOVA with Bonferroni post-tests when compared to the zero time point (* P*** P****P<0.0001). C) The box and whiskers plot demonstrates the overall proportion of SYTO 9 (green) only staining, compared to SYTO 9 and PI (red) staining populations of cells in water for the 8-week time course.