3rd December 2019

microscopemaster

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What is the purpose of a gram stain?

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Purpose, Procedure and Preparation. Gram stain is probably one of the most commonly used staining procedures used in the field of microbiology. It is one of the differential stains that are used to characterize bacteria in one of two groups: either gram positive bacteria or gram negative bacteria.

In this regard, what does Gram stain tell you?

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.

Why is staining so important?

Stains are classified broadly as basic, acidic, or neutral stains. The chemical nature of the cells under examination determines which stain is selected for use. Cell staining is important in the diagnosis of microorganisms because bacteria can be identified by the color differentiation of stains (dyes).

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What is the function of safranin in the Gram stain?

The purpose of safranin in the Gram's stain procedure is it directly stains the gram- negative bacteria that became decolorized. Gram-positive cells stain purple because they retain the crystal-violet dye in their cell walls. They also stain purple because of the thick layer of peptidoglycan in their cell walls.

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What is the purpose of using a simple stain?

The simple stain can be used to determine cell shape, size, and arrangement. True to its name, the simple stain is a very simple staining procedure involving only one stain. You may choose from methylene blue, Gram safranin, and Gram crystal violet.

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What is a Gram stain used for?

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.

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What is the purpose of the crystal violet stain?

Gram-positive cells stain purple because they retain the crystal violet-iodine complex in their cell walls. Also because the crystal violet is a positive charge dye which is attracted to the negative charge in the cell and also the thicker peplidoglycan layer helps retain the dye more.

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What is the purpose of iodine in the Gram stain procedure?

What is the purpose of iodine in the Gram's stain procedure? It forms an insoluble crystal violet iodine complex which allows the stain to be retained better. E. What is a mordant? It is a chemical that can deepen the reaction of another dye.

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Why is Gram staining important for classifying bacteria?

Importance of a Gram Stain: The Gram stain is a very important preliminary step in the initial characterization and classification of bacteria. It is also a key procedure in the identification of bacteria based on staining characteristics, enabling the bacteria to be examined using a light microscope.

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What is the use of safranin?

Safranin is used as a counterstain in some staining protocols, colouring all cell nuclei red. This is the classic counterstain in both Gram stains, and endospore staining. It can also be used for the detection of cartilage, mucin and mast cell granules.

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What does it mean to be Gram positive or negative?

This stain will either stain the cells purple (for positive) or pink (for negative). Gram-positive bacteria have a very thick cell wall made of a protein called peptidoglycan. These bacteria retain the crystal violet dye (one of the 2 main chemicals used for gram staining).

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How is Gram staining done?

Place slide with heat fixed smear on staining tray.
Gently flood smear with crystal violet and let stand for 1 minute.
Tilt the slide slightly and gently rinse with tap water or distilled water using a wash bottle.
Gently flood the smear with Gram's iodine and let stand for 1 minute.

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What is crystal violet used for in Gram staining?

Gram-positive bacteria have a thick mesh-like cell wall made of peptidoglycan (50–90% of cell envelope), and as a result are stained purple by crystal violet, whereas gram-negative bacteria have a thinner layer (10% of cell envelope), so do not retain the purple stain and are counter-stained pink by safranin.

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What is the most critical step in the Gram stain and why?

The most critical phase of the Gram stain procedure is the decolorization step, which is based on the ease with which the crystal violet-iodine complex is released from the cell. Over-decolorizing will result in the loss of the primary stain, causing Gram positive bacteria to appear Gram negative.

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What is the function of the Counterstain in the Gram stain?

Examples include the malachite green counterstain to the fuchsine stain in the Gimenez staining technique and the eosin counterstain to haematoxylin in the H&E stain.In Gram staining, crystal violet stains only Gram-positive bacteria, and safranin counterstain is applied which stains all cells, allowing the

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What differentiates Gram positive bacteria from Gram negative bacteria?

Danish scientist Hans Christian Gram devised a method to differentiate two types of bacteria based on the structural differences in their cell walls. In his test, bacteria that retain the crystal violet dye do so because of a thick layer of peptidoglycan and are called Gram-positive bacteria.

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Why are most staining procedures not useful for living cells?

Cell staining is a technique that can be used to better visualize cells and cell components under a microscope. By using different stains, one can preferentially stain certain cell components, such as a nucleus or a cell wall, or the entire cell.

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What is a gram negative organism?

Example species. The proteobacteria are a major phylum of gram-negative bacteria, including Escherichia coli (E. coli), Salmonella, Shigella, and other Enterobacteriaceae, Pseudomonas, Moraxella, Helicobacter, Stenotrophomonas, Bdellovibrio, acetic acid bacteria, Legionella etc.

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Why are the results of a Gram stain from a patient important?

If your gram stain results are negative, it means no bacteria were found in your sample. If they're positive, it means bacteria were present. Because of the staining technique used, gram-positive bacteria will appear purple under a microscope and gram-negative bacteria will appear pink.

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What is meant by differential staining?

Differential Staining is a staining process which uses more than one chemical stain. Gram staining uses two dyes: Crystal violet and Fuchsin or Safranin (the counterstain) to differentiate between Gram-positive bacteria (large Peptidoglycan layer on outer surface of cell) and Gram-negative bacteria.

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What does it mean to have gram positive cocci?

A few examples of some medically significant bacteria and what they look like on a Gram stain include: Gram-positive cocci—Staphylcoccus aureus (Staph aureus) can cause skin infections and toxic shock syndrome; Streptococcus pneumoniae can cause pneumonia.

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What is gram positive bacteremia?

In the classical sense, six Gram-positive genera are typically pathogenic in humans. Two of these, Streptococcus and Staphylococcus, are cocci (sphere-shaped). Gram-positive bacteria are capable of causing serious and sometimes fatal infections in newborn infants.

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