Why are two different species of bacteria used in the acid-fast stain procedure?
ID: 162095 • Letter: W
Question
Why are two different species of bacteria used in the acid-fast stain procedure? Make a chart for the acid-fast stain that lists the primary stain, mordant, decolorizer, and counterstain. (You may need to use an additional sheet of paper). Which type of stains (acidic or basic) enter bacterial cells and why? Describe the appearance of capsules for a specimen properly stained with the capsule stain procedure. Identify two methods for determining whether bacteria exhibit motility. Why might organisms that are normally motile display a loss of motility (under what circumstances)? Distinguish motility from Brownian motion, as observed with a microscope. Sketch both a positive and a negative motility stab. Describe how motility can be an important factor in causing disease.Explanation / Answer
Acid fast staining helps the staining of bacteria with more lipids in their cell walls like Mycobacterium. In this method the carbol fuschin solubilises the lipid content and heat helps to penetrate the cell walls more. Acid fast bacteria resist the following decolorisation due to lipid content and non acid fast bacteria will get decolorised.
2. Primary stain- Carbol fuschin- solubilises lipids
Decoloriser- 3%HCL in 95% alcohol - acid alcohol - decolorisation of non acid fast bacteria
Counter stain- methylene blue- gives colour to non acid fast bacteria
3. Acidic dyes can stain bacteria well because they have anionic chromophophore ( negative charges) and is attracted towards the cytoplasm which is cationic.
4. Capsule or slime layer is the gelatinous outer layer of bacteria. After staining we can see a clear hallow zone around the bacteria in a dark background.
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