Negative staining employs the use of an acidic stain and, due to repulsion between the negative charges of the stain and the bacterial surface, the dye will not penetrate the cell. In negative staining, the results yield a clear cell with a dark background.

What type of staining is negative staining?

Negative staining requires an acidic dye such as India Ink or Nigrosin. India Ink or Nigrosin is an acidic stain. This means that the stain readily gives up a hydrogen ion (proton) and the chromophore of the dye becomes negatively charged.

What are examples of negative stain?

Some suitable negative stains include ammonium molybdate, uranyl acetate, uranyl formate, phosphotungstic acid, osmium tetroxide, osmium ferricyanide and auroglucothionate. These have been chosen because they scatter electrons strongly and also adsorb to biological matter well.