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Stain or dye is the synthetic chemical which is derived from nitrobenzene or aniline. Stains are used commonly in microbiology to increase the contrast between microorganisms or parts of its and the background, so that it can be easily visible.
Types of Staining Techniques Used in Microbiology Written by Acharya Tankeshwarin Staining Techniques Last Updated October 4, 2022 Structural details of organisms cannot be seen under a light microscope due to a lack of contrast. Hence, we use dyes to stain cells. Dyes bind with cellular constituents producing color contrast and increasing their visibility. Positively charged (cationic) dyes such as methylene blue, crystal violet, safranin, etc bind with negatively charged cellular constituents such as nucleic acids and acidic polysaccharides and the cell surface of bacteria. Based on the types and number of dyes used, staining can be categorized into different types.
They are colored organic compounds used for staining microorganisms. Chemically, Stains= Benzene ring+ Chromophore + Auxochrome
According to nature of stain, it can be classified into:
1. Acidic Dyes:
It is dye which has negative charge so they bind to positively charged cell structures like some proteins. Acidic dyes are not very often used in Microbiology lab.except to provide background staining like Capsule staining. Examples: Nigrosine, Picric acid, Eosin, Acid fuschin, India ink etc.
2. Basic Dyes:
This dye have positive charge & bind to negatively charged molecules(nucleic acid, -COOH -OH). Since, surface of bacterial cells are negatively charged(due to Teichoic acid), basic dyes are most commonly used in bacteriology. Examples: Crystal Violet, Methylene Blue, Safranin , basic fuschin.
3. Neutral Dyes:
They are usually formed from precipitation in which are produced when aqueous acidic & basic stains are combined. Neutral dyes stains nucleic acids, & cytoplasm. Eg; Eosinate of Methylene blue, Giesma stain.
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Cite this page:
BS Media. “Stains / Dyes.” BioScience. BioScience ISSN 2521-5760, 27 February 2017. <https://www.bioscience.com.pk/en/topics/microbiology/mode-of-action-of-stains>.
BS Media. (2017, February 27). “Stains / Dyes.” BioScience. ISSN 2521-5760. Retrieved January 27, 2023 from https://www.bioscience.com.pk/en/topics/microbiology/mode-of-action-of-stains
BS Media. “Stains / Dyes.” BioScience. ISSN 2521-5760. https://www.bioscience.com.pk/en/topics/microbiology/mode-of-action-of-stains (accessed January 27, 2023).
