Difference between Simple and Differential Staining

Table of Contents

• What is Simple Staining?
• What is Differential Staining?
• Gram’s Staining
• Acid Fast Staining
• Simple vs Differential Staining
• Frequently Asked Questions

What is Simple Staining?

Simple staining is the procedure of using only one stain on the slide. This staining either colours the cells or colours the background. Hence, simple staining can be used to analyse only one organism per slide. Simple staining can be of two types: simple positive staining and simple negative staining.

In simple positive staining, basic dyes such as methylene blue or crystal violet are used. The basic dye gets attracted to the negatively charged genetic material of the microbial cytoplasm.

Alternatively, in simple negative staining, acidic dyes such as nigrosin or congo red are used. These dyes are repelled by the negatively charged genetic material of the bacteria and collect around bacterial cells. This gives a colour to the background and leaves the microbial cells colourless.

What is Differential Staining?

Differential staining is a procedure where more than one dye is used to differentiate between different types of microorganisms on a slide. This type of staining helps to differentiate between cell types and cell structures.

Gram’s Staining

Gram’s staining is the most common example of differential staining. This staining method divides bacteria into gram-positive and gram-negative bacteria. It uses crystal violet as the primary stain, iodine as mordant and safranin as counterstain.

The gram-positive bacteria retain the primary stain even after washing the slide with alcohol. On the other hand, gram-negative bacteria lose the primary stain and instead take up the counterstain. Hence, on analysing the stained slide, one can observe gram-positive bacteria in blue-purple colour and the gram-negative bacteria in red colour.

Refer: Difference between Gram-positive and Gram-negative Bacteria

Acid Fast Staining

It is a differential staining method that is used to differentiate Mycobacterium from other bacterial species. The cell wall of the Mycobacterium species contains large amounts of lipids called mycolic acids. These acids resist staining by ordinary Gram’s stains.

In acid-fast staining, carbol fuchsin is applied as the primary dye and then washed off with alcohol. Methylene blue or malachite green is used as the counterstain. On observing the slide, one can see the Mycobacterium species in red colour and other bacterial species in blue or green colour.

Simple vs Differential Staining

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Also Read:

• Classification of Microorganisms – NEET Biology Notes
• An Overview of Useful and Harmful Microorganisms