Procedure: . Make a smear and label it. . Allow the smear to dry in air. . Fix the smear over a flame. .Apply a few drops of positive simple stain like 1% methylene blue, 1% carbolfuchsin or 1% gentian violet for 1 minute. . Wash off the stain with water. . Air-dry and examine under the oil immersion objective.
Negative staining: The dye stains the background and the bacteria remain unstained. Eg. Indian ink stain Negrosin stain
2. Differential staining method Multiple stains are used in differential staining method to distinguish different cell structures and/or cell types. Eg. Gram stain and Ziehl- Neelson stain
A. Gram staining method Developed by Christian Gram. Most bacteria are differentiated by their gram reaction due to differences in their cell wall structure. Gram-positive bacteria are bacteria that stain purple with crystal violet after decolorizing with acetone-alcohol. Gram-negative bacteria are bacteria that stain pink with the counter stain (safranin) after losing the primary stain (crystal violet) when treated with acetone-alcohol.