Stains And Staining Techniques In Microbiology Pdf

stains and staining techniques in microbiology pdf

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Uses an acidic stain: Congo red or Nigrosin and a basic stain: crystal violet or safranin. Simple Stains: Crystal Violet, Methylene Blue, Safranin Used to provide color to otherwise transparent bacterial cells Can be used to determine cell size, morphology and arrangement.

3.4: Summary of Common Bacterial Staining Techniques

Important information such as shape and degree of motility can be obtained by observation of living bacteria with the phase contrast or dark field microscope. However bacteria are routinely stained with different dyes in order to reveal different properties and to enhance contrast for viewing with conventional bright field microscopy. A number of stains have been developed to distinguish spores, nuclear bodies, capsules, and characteristics of the cell wall. The staining methods we will use kill the bacteria, reducing the risk of infection by pathogenic organisms. Since the rigid cell walls of bacteria prevent distortion of morphology upon drying, samples can be spread onto a glass slide and air dried, then fixed to the surface by passing the slide quickly through a flame, melting the complex carbohydrates of the cell walls to the glass and killing the cells. The Gram stain is routinely used as an initial procedure in the identification of an unknown bacterial species.

3.4: Summary of Common Bacterial Staining Techniques

Show Caption Hide Anthrax gram stain. Gram staining is a common technique used to differentiate two large groups of bacteria based on their different cell wall constituents. The Gram stain procedure distinguishes between Gram positive and Gram negative groups by coloring these cells red or violet. Gram positive bacteria stain violet due to the presence of a thick layer of peptidoglycan in their cell walls, which retains the crystal violet these cells are stained with. Alternatively, Gram negative bacteria stain red, which is attributed to a thinner peptidoglycan wall, which does not retain the crystal violet during the decoloring process.

A special staining technique is also used to examine bacterial spores. Malachite green is used with heat to force the stain into the cells and give them color. A counterstain, safranin, is then used to give color to the nonsporeforming bacteria. At the end of the procedure, spores stain green and other cells stain red.

3.4: Summary of Common Bacterial Staining Techniques

In their natural state, most of the cells and microorganisms that we observe under the microscope lack color and contrast. This makes it difficult, if not impossible, to detect important cellular structures and their distinguishing characteristics without artificially treating specimens. We have already alluded to certain techniques involving stains and fluorescent dyes, and in this section we will discuss specific techniques for sample preparation in greater detail.

Staining Methods – Simple Staining, Negative Staining, Gram’s Staining and Acid-Fast Staining

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Stain – Majority of the stains used for staining bacteria are of the basic type as ➢A simple staining technique that stains the bacterial cells in a single color.



PDF | The correct identification of micro organisms is of fundamental importance Some staining techniques, such as the Gram and Ziel Neelsen stains, although (e.g. agriculture, clinical microbiology and food production).

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The microscope is a very important tool in microbiology, but there are limitations when it comes to using one to observe cells in general and bacterial cells in particular.

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