The LIVE/DEAD® BacLight™ Bacterial Viability and Counting Kit allows researchers to reliably distinguish and quantitate live and dead bacteria with the aid of a flow cytometer, even in a mixed population containing a range of bacterial types. This kit uses a mixture of two nucleic acid stains - green-fluorescent SYTO® 9 dye and red-fluorescent propidium iodide - for viability determinations, and a calibrated suspension of microspheres for accurate sample volume measurements.