The Cell-Check™ Viability/Cytotoxicity Kit for Bacteria Cells provides two-color fluorescence staining on both live (green) and dead (red) bacteria using two probes, NucView Green and Propidium iodide. NucView Green is a green-fluorescent nucleic acid dye that stains both live and dead bacteria with intact and damaged cell membranes. Propidium iodide is a red-fluorescent nucleic acid dye that stains only dead bacteria with damaged cell membranes. With an appropriate mixture of NucView Green and Propidium iodide, bacteria with intact cell membranes is stained fluorescent green, whereas bacteria with damaged cell membranes is stained fluorescent red. The kit is suitable for use with fluorescence microscopes and flow cytometers. The assay principles are general and applicable to most bacteria types.