24-What is the mordant in acid- fast staining? A. Basic fuchsin B. Heat C. Methy

Question

24-What is the mordant in acid- fast staining? A. Basic fuchsin B. Heat C. Methylene blue D. Acid-alcohol 25- Which stain is a differential stain? ?.gram stain B. capsule stain C. acid fast stain D. both a and c 26-Most bacteria belong to this metabolic group A. Chemoorganotrophs B. Chemolithotrophs C. Photoheterotrophs D. None of these 27-Agar, a complex polysaccharide is isolated from A. Seaweeds B. Tree barks C. Tree stem D. None of these 28-What are two commonly used isolation procedures for obraining pure cultures A Streak and pour plate B. Streak and loop plabe C. Quadrant and radiant streak D. All of the above 29-Molds are fungi that grow in the fors of multicellular filaments called A. Septa B. Hyphac C. Blastospore D. Pseudobhyphac 30-Helicobacter pylori is a microacrophile that prefer to grow in A. No oxygen B. 2-10 % ofoxygen C. 20%ofoxygen D. Band C 31-Fluid thioglycollate medium (FTM) is a rich medium that supports the growth of A. Acrobic organisms B. C. D. Anacrobic organisms Both A and B None of the above 32-What is a colony? A A mass of cells that derived from a single cell B. C. D. Cells from different species A and B None of these

Explanation / Answer

Ans. #24. B. Heat. Heat acts as mordant in acid fast staining.

Basic fuchsin acts as primary stain, acid-alcohol acts as decolorizer, and methylene blue acts as counterstain.

#25. D. Both a and c. A differential stain differentiate two or more groups/types of cells from each other based on certain distinguishing characteristics. Both Gram-stain and Acid-fast stain are differential stains because they differentiate bacteria into respective types-

# Gram-positive bacteria appears violet whereas Gram-negative cells appear pink.

# Acid-fast stain is used to differentiate acid-fast bacteria from non-acid fast. The acid-fast bacteria appear bright red or purple by retaining Congo red whereas the non-acid-fast cells appear blue by getting stained with methylene blue.

# Capsule stain is a simple stain. It does not differentiate cells into two or more types upon staining.

# 26. A. Chemoorganotroph. Most bacteria are Chemoorganotroph or Chemoheterotrophs.

# 27. A. Seaweeds. Agar is extracted from red algae Gelidium amansii and Kappaphycous (a type of seaweeds)

#28. A. Streak and pour plate. Pure cultures can be isolated by streak-plate, pour plate or spread plate techniques.

#Option B- Incorrect. There is no such method called loop plate to isolate pure colonies.

# Option C- Incorrect. Quadrant and radiant streak methods are grouped under the same method – streak method.

#29. B. Hyphae. A long branched threadlike filament of fungal cells is called hyphae.

# Septa is the cross-wall between two adjacent fungal cells in the mycelium.

# Blastospores are NOT the multicellular filamentous form of fungal cells.

# Pseudohyphae are distinct from true hyphae.

#30. B. 2-10%. A microaerophile bacteria exhibits optimum growth is lower O2 in the medium than the atmosphere, usually 2-10% (atmosphere has around 21% O2). Higher O2 may kill such microbes.

#31. C. Both A and B. FTM can be used to cultivate both aerobic (microaerophiles) and anaerobic organisms.   

#32. A. A mass of cells that derived from a single cell.

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