Figure 2.

Sphingosine abrogates the metabolic activity of P. aeruginosa and S. aureus. P. aeruginosa (P.a.) strains 762 and American Type Culture Collection (ATCC) 27853 or S. aureus (S.a.) strain DH was treated with 1 or 10 μm SPH or OGP, the solvent of sphingosine, at the corresponding concentrations. Samples were then incubated with the oxidized, nonfluorescent form of C₁₂-resazurin, and the metabolic activity was determined with flow cytometry by measuring the generation of fluorescent C₁₂-resorufin. The studies showed that sphingosine results in a very rapid decrease in bacterial metabolic activity. Either Triton or nisin was added as a positive control for membrane permeabilization and disruption of bacterial metabolism. Fluorescence intensity is given in arbitrary units (a.u.). Displayed are the means ± S.D. of four independent experiments each. ***, p < 0.001, ANOVA.