When phloxine B is subjected to light, debromination occurs and free radicals and singlet oxygen are formed.

This polysaccharide-coated lipid bilayer creates a permeability barrier that prevents efficient uptake of the compound.

Addition of EDTA, which is known to strip the lipopolysaccharides and increase membrane permeability,[9] removes the phloxine B resistance and allows gram-negative bacteria to be killed as well.

Dead yeast cells lose membrane integrity, so phloxine B can enter and stain the intracellular cytosolic compounds.

[10] The same principle can be applied at higher throughput by fluorescence-activated flow cytometry (FACS), where all phloxine B-stained cells in a sample are counted.