Uses carbolfuchsin, acid-alcohol, and methylene blue Distinguishes between active metabolic cells and dormant structures A chemical is used as a mordant Differentiates cells with high lipid content in cell wall Result is purple and red/pink cells Gram Stain (1/3) Acid-Fast Stain (2/3) Spore Stain (3/3)
Added by Hunter R.
Close
Step 1
Step 1: Gram Stain (1/3): - Result is purple and red/pink cells - A chemical is used as a mordant Show more…
Show all steps
Your feedback will help us improve your experience
Adi S and 100 other Biology educators are ready to help you.
Ask a new question
Labs
Want to see this concept in action?
Explore this concept interactively to see how it behaves as you change inputs.
Key Concepts
Recommended Videos
As discussed previously, the cell walls of acid-fast bacteria are extremely hydrophobic due to large amounts of mycolic acid, so they repel the basic dyes used for most staining procedures. For example, crystal violet and safranin (used in the Gram Stain) do not bind to acid-fast cells. Therefore, we need to use a different staining procedure when patients are suspected of having an acid-fast bacterial infection, like tuberculosis. The Acid-Fast Stain is another differential stain; it is used to detect cells that are able to retain the primary stain. Here are the basic steps: 1. Make a heat-fixed smear of the sample on the slide. 2. Add a lipid-soluble primary stain while also heating the sample. The heat allows the dye to penetrate the waxy cell wall. The primary stain that is typically used is called carbol fuchsin and it stains all cells a hot pink (fuchsia) color. 3. Decolorization with an acid/alcohol mix removes the color from the non-acid-fast bacteria. This is where acid-fast bacteria get their name. They are able to "hold fast" to the carbol fuchsin stain; in other words, once the lipid-soluble dye is stuck to the waxy mycolic acid in acid-fast cells, they don't let it go during this decolorization step. 4. In contrast, all acid-fast negative cells (like Gram-positive and Gram-negative bacteria) are decolorized during this step, leaving them colorless. 5. Then, a counterstain, methylene blue in this case, is used to give color/contrast to all of the acid-fast negative cells. Remember, the methylene blue is a simple stain and will be repelled by any acid-fast cells during this step, so these cells remain the hot pink color because they are still holding onto the primary stain. Answer the following questions: Both acid-fast and non-acid-fast cells are stained by carbol fuchsin. How is it then, that we can use it as a differential stain? How is this similar to the Gram stain? (Discuss the use of primary stains and decolorizers in both stains). The differential step of any procedure is the step when the two different types of cells start to look differently from each other (in this case, the Gram-positive and Gram-negative cells). Which step of the acid-fast staining procedure would be considered the differential step? Explain your answer.
Adi S.
A bacterial smear was first stained with steaming malachite green for 3-5 min and then counterstained with safranin. The illustration of the four cells below is a sample of what was seen in the microscope using the oil immersion lens. (1) What is the name of this staining procedure? (2) What are the structures that are stained green? (3) What are stained pink? a. (1) Gram stain, (2) endospores, (3) vegetative cells b. (1) spore stain, (2) endospores, (3) vegetative cells c. (1) spore stain, (2) vegetative cells, (3) endospores d. (1) Gram stain, (2) Gram positive cells, (3) Gram negative cells
Suman K.
Move the descriptions into the correct boxes to assess your understanding of the differential staining techniques, including acid-fast stain, and spore stain. - Does not require heat to be used in staining process - Result is purple and red/pink cells - Distinguishes between active metabolic cells and dormant structures - Uses basic fuchsin, acid-alcohol, and methylene blue - Differentiates cells with high lipid content in cell wall - A chemical is used as a mordant - Differentiates cells based on thickness of peptidoglycan layer - Important diagnostic tool in Mycobacterium infections - Uses malachite green - Spore Stain - Gram Stain - Acid-Fast Stain - Reset
Recommended Textbooks
Biology for AP Courses
Objective Biology for NEET
Introduction to General, Organic and Biochemistry
Transcript
Watch the video solution with this free unlock.
EMAIL
PASSWORD