Endy:NPE flow cytometer

Sheath fluid

The special marine diluent functions as sheath fluid and resuspension medium when analyzing bacterial cells. It has a high osmolarity (~733 mosM according to M.Brochu Sr. at NPEsystems); compare with ~300 mosM for typical saline like 1xPBS. The high osmolarity permits better signal on the electronic volume channel for size < 1um; lower osmolarity would give noisier results. A concern, however, is that a high osmolarity solution will lead to shrinkage of the cells as compared to normal growth medium. Diluting the diluent can help mitigate this effect, but will probably increase noise. If you plan to study cells with volume > 1um3, the special marine diluent may be diluted by ~30% and still give acceptable (not results. However, I haven't tried that yet. Another solution is to run cells immediately after resuspension in the Special Marine Diluent.