Ruthenium red is a polycationic stain used to visualize acid polysaccharides on the outer surface of cells. Ruthenium red staining followed by electron microscopic analysis was used to demonstrate the presence of an external glycoprotein layer surrounding the spore of both Bacillus anthracis and Bacillus subtilis.

Application

Ruthenium red (RR) is a polycationic dye that has been used to sustain negatively charged molecular species in tissue sections (Luft, 1971). In the electron microscope, stained areas are electron dense and thus are easily distinguished from those that are unstained.