Safranin is the secondary dye used in the Gram stain. This dye will stain the decolorized Gram-negative cells, which will appear in pink.
What reagent is applied to Decolorize the Gram-negative bacteria and thus differentiate it from the gram positive?
Add Gram’s iodine for 1 minute- this is a mordant, or an agent that fixes the crystal violet to the bacterial cell wall. Rinse sample/slide with acetone or alcohol for ~3 seconds and rinse with a gentle stream of water. The alcohol will decolorize the sample if it is Gram negative, removing the crystal violet.
How can you differentiate between gram positive and Gram-negative bacteria in the experiment?
Gram positive bacteria have a thick peptidoglycan layer and no outer lipid membrane whilst Gram negative bacteria have a thin peptidoglycan layer and have an outer lipid membrane.
What is used to Decolorize a Gram stain?
The decolorizing agent, (ethanol or an ethanol and acetone solution), interacts with the lipids of the membranes of both gram-positive and gram-negative Bacteria. The outer membrane of the gram-negative cell is lost from the cell, leaving the peptidoglycan layer exposed.
Which reagent used in the Gram stain makes this stain an example of a differential stain?
Flagella Staining
| Table 3. Differential Stains | |
|---|---|
| Stain Type | Specific Dyes |
| Gram stain | Uses crystal violet, Gram’s iodine, ethanol (decolorizer), and safranin |
| Acid-fast stain | After staining with basic fuchsin, acid-fast bacteria resist decolonization by acid-alcohol. Non-acid-fast bacteria are counterstained with methylene blue. |
What is used to Decolorize in the Gram stain method quizlet?
What is the decolorizer? Decolorizer: In order to remove the primary dye from the Gram-negative cells, 95% ethanol is used as a decolorizer.
Which reagent is responsible for staining Gram-negative bacteria pink?
Safranin is used as a counterstain, staining the Gram-negative bacteria, pink. Like crystal violet, it is a positively charged molecule that binds to negative bacterial cell wall structures.
How do Gram positive bacteria differ from gram negative bacteria quizlet?
Gram positive bacteria have lots of peptidoglycan in their cell wall which allows them to retain crystal violet dye, so they stain purple-blue. Gram negative bacteria have less peptidoglycan in their cell wall so cannot retain crystal violet dye, so they stain red-pink.
How do Gram positive and gram negative bacteria differ in their cellular structure quizlet?
How do gram-positive and gram-negative bacteria differ in cellular structure, and how does this contribute to their differential staining properties? Gram-positive bacteria have a thicker layer of peptidoglycan that retains the crystal violet-iodine complex. You just studied 20 terms!
How might the physical differences between Gram positive and gram negative bacteria contribute to differences in chemical resistance?
How might the physical differences between gram positive and gram negative bacteria contribute to differences in chemical resistances? how the affect the cell wall, gram pos bacteria have thicker peptidoglycan so will be more resistant to chemicals.
What is negative staining in microbiology?
Negative staining employs the use of an acidic stain and, due to repulsion between the negative charges of the stain and the bacterial surface, the dye will not penetrate the cell. In negative staining, the results yield a clear cell with a dark background.
What is the secondary stain used that colors the decolorized Gram-negative bacteria pink?
The counter stain safranin (secondary stain) is used to create good contrast between Gram-positive and Gram-negative bacteria. Decolorized Gram-negative cells retain the safranin stain and appear reddish-pink upon completion of the procedure.
Which reagent is responsible for staining Gram-positive bacteria purple?
Staining mechanism
| Application of | Reagent | Cell color |
|---|---|---|
| Gram-positive | ||
| Primary dye | crystal violet | purple |
| mordant | iodine | purple |
| Decolorizer | alcohol/acetone | purple |
What color do Gram-negative bacteria stain?
A Gram stain is colored purple. When the stain combines with bacteria in a sample, the bacteria will either stay purple or turn pink or red. If the bacteria stays purple, they are Gram-positive. If the bacteria turns pink or red, they are Gram-negative.
What types of dyes are used for negative staining?
Negative staining requires an acidic dye such as India Ink or Nigrosin. India Ink or Nigrosin is an acidic stain.
What dye in the Gram stain do Gram-negative bacteria retain?
crystal violet dye
The basic principle of gram staining involves the ability of the bacterial cell wall to retain the crystal violet dye during solvent treatment.
What is the best procedure for decolorization quizlet?
What is the best procedure for decolorization? Add decolorizing agent until run-off is clear…….. This method allows the decolorizing agent to dissolve the outer membrane of Gram-negative cells and rinse out the crystal violet from the thin layers of peptidoglycan. This causes the run-off to be purple.
What is negative staining quizlet?
Negative stain is used when viewing bacteria by wet mount or hanging drop slide to view bacterial motility.Negative stains will not penetrate and stain the bacterial cell wall because they have a negative charge and therefore are repelled by the negative charge of the bacterial cell.
Which reagent is used as a counterstain quizlet?
The counterstain is Gram Safranin. The decolorizer is Ethanol. It is added to chemically change the shape of the dye molecule and trap it in the cell wall. Iodine is used in the Gram stain.
What are the reagents used in Gram staining?
Reagents needed for Gram staining include:
- Crystal violet (primary stain) [1]
- Gram’s iodine solution (the mordant) [1]
- Acetone/ethanol (50:50 v:v) (the decolorizer) [1]
- 0.1% basic fuchsin solution (the counterstain) [1]
- Water.
What are the reagents used in Gram staining and their functions?
The first reagent is called the primary stain. Its function is to impart its color to all cells. The second stain is a mordant used to in- tensify the color of the primary stain. In order to es- tablish a color contrast, the third reagent used is the decolorizing agent.
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