Molecular Probes™ CountBright™ Absolute Counting Beads, for flow cytometry

Prior to taking an aliquot, make certain to thoroughly mix the beads. This may also be caused if the beads were ever frozen or the stock solution has any microbial contamination.

You may use any physiological buffer or media in a pH range from pH 4 to 10. Avoid extremes of pH and high salt concentrations.

Here are the differences:

CountBright Plus Absolute Counting Beads:
Bead Size: 4 µm
Excitation Range: 385 - 810 nm
Emission Range: 385 - 860 nm

CountBright Absolute Counting Beads:
Bead Size: 7 µm
Excitation Range: 350 - 635 nm
Emission Range: 350 - 810 nm

The green dye in the kit will label all the cells as it is a cell-permeant nucleic acid stain. The red dye is not cell permeant, and will only stain the cells with compromised membranes (dead cells). Therefore, any cells with red signal will be considered dead. It is possible that you will have some cells that are only red, some that are red and green, and some that are only green. Sometimes the red dye will displace the green dye. In any case, any red cells are dead.

Also, the green dye emission may bleed through into the red channel. Do a single-color staining and examine under both green and red filter sets to determine the level of bleedthrough. To avoid this bleedthrough, use a lower concentration of dye, and, if possible, use narrow bandpass filters.

There are several options. We have two fluorescence based kits that are useful for bacterial counting: Live/Dead BacLight Bacterial Viability and Counting Kit, for flow cytometry (Cat. No. L34856) and Bacteria Counting kit, for flow cytometry (Cat. No. B7277). Another option is the Flow Cytometry Sub-micron Particle Size Reference Kit (Cat. No. F13839).