Figure 5. Effect of Carolacton-treatment on the membrane integrity and membrane potential of S. pneumoniae TIGR4.

(A) Cells grown with 0.25 μg/ml Carolacton (+) and controls (−) were stained with Syto 9/PI and analysed using flow cytometry as exemplified in Fig. S8. Error bars of stained heat-killed controls (red bars) are not visible, as continuously more than 99.9% of all heat-treated cells were killed and emitted red fluorescence. (B) Changes in membrane potential were quantified by flow cytometric analysis of DiOC₂(3)-stained planktonic cells. The relative membrane potential was calculated ratiometrically. Analyses were carried out with 30 μM DiOC₂(3). Heat-killed cells served as a control for fully depolarized cells. The bar charts present the average of three biological replicates (±s.d.). P value: n.s. = > 0.05; ** = < 0.01; *** = < 0.001; two-tailed Student’s t-test.