viva questions on staining techniques.pptx

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1. VIVA QUESTIONS ON STAINING TECHNIQUES Microbial Concepts

2. Q. What is objective of staining? Improves visibility by greater contrast between the organism and the background, differentiate various morphological types (by shape, size, arrangement, etc.). Q. What are the functions/Role of fixative? It kills the organisms; (2) it causes the organisms to adhere to the slide; and (3) it alters the organisms so that they more readily accept stains (dyes)”. Q. What is Mordant? It is a chemical that forms an insoluble complex with the stain and fixes it or causes the stain to penetrate more deeply into the cell. Ex. Gram’s iodine Q. What is Decolorizer? It is a chemical used to remove the excess stain in indirect regressive staining. ex, Ethanol in Gram’s staining.

3. Q. Define stain: STAIN is defined as coloring agent used for coloring biological material. A stain is an organic compound containing a benzene ring plus a chromophore and an auxochrome group. Q. In capsule staining Congo red stains what? –Background Q. Why colour change is seen in case of congo red? Due to acetic acid pH is shifted to the acidic side and due to which congo red stain turns red to blue in colour that is why the colour of background changes from red to blue in colour . Q. Which dye stains endospore in Schaeffer and Fultons Method ? - Malachite green Q. Why heating is required in endospore staining? Heating will make the spore wall more permeable to the malachite green which was previously resistant.

4. Q. In Dorners Method of endospore staining which dye sol n stain’s background? - Nigrosin soln Q. What is Acid Fastness? Acid-fastness is a physical property of certain bacterial, has resistance to decolorization by acids during staining procedures. Due to the unique cell wall structure, we can identify these bacteria using a stain called an acid fast stain. Q. What is used as Mordant in ZN staining ? -Steam Heat / Heat. Q. What is used as Decolorizer in ZN staining? - depending on sample it can be 1% or 5% or 20% H2SO4 and 95% Alcohol. Q. What is used as Counter Stain in ZN staining? - Malachite green or Methylene blue.

5. Q. In Gram staining what is used as mordent? - Grams Iodine Q. Safranin in Gram staining is a primary stain or counter stain? – Counter stain Q. Gram staining differentiates bacteria based on? – Cell wall composition Q. What is a difference between Cell wall composition of Gram positive and Gram negative bacteria? Gram-negative bacteria has a thin peptidoglycan cell wall, and is surrounded by an outer membrane containing lipopolysaccharide.  Gram-positive bacteria lack an outer membrane but are surrounded by layers of peptidoglycan- many times thicker than is found in the Gram-negatives. Q. What is Monochrome staining? Using one dye for staining purpose either primary or counter stain just to study shape or morphology.

6. Q. Alternative primary stain in Gram staining? – Gentian violet or Methyl violet Q. Alternative counter stain in Gram staining? – Diluted carbol fuchsin or neutral red. Q. What is the principle of Leifson method of Flagella staining? The Leifson flagella stain method uses tannic acid and a dye. When bacterial flagella absorbs this tannic acid and a dye, it forms a colloidal precipitate as a result the flagella is colorized and as well as increase in diameter, thus amenable to viewing by light microscopy.  LIKE SHARE n SUBSCRIBE