Simple Staining 50 FAQ and 40 MCQs:
Simple Staining 50 FAQ :
What is simple staining?
Simple staining uses a single dye to highlight bacterial morphology and arrangement.
What is the purpose of simple staining?
To visualize bacterial shape (cocci, bacilli, spirilla) and arrangement (chains, clusters).
What bacterial features can be observed with simple staining?
Cell shape (morphology) and arrangement (e.g., single, diplo-, strepto-, staphylo-).
What features CANNOT be determined with simple staining?
Cell wall structure (Gram-positive/Gram-negative), capsules, endospores, or flagella.
What are the types of simple staining?
Positive staining (dyes cells) and negative staining (dyes background).
What are common basic dyes used in simple staining?
Methylene blue, crystal violet, safranin, carbol fuchsin.
What are common acidic dyes used in negative staining?
Nigrosin, Congo red, eosin.
Why are basic dyes preferred for simple staining?
Bacterial cells are negatively charged, attracting positively charged basic dyes.
What is the charge of bacterial cells?
Negative (due to nucleic acids and cell wall components).
What is the difference between simple and differential staining?
Simple staining uses one dye, while differential staining (e.g., Gram stain) uses multiple dyes to classify bacteria.
What are the steps in simple staining?
Smear preparation → Heat fixation → Staining → Washing → Drying → Microscopy.
Why is heat fixation important?
Kills bacteria, adheres them to the slide, and preserves morphology.
How is a bacterial smear prepared from a liquid culture?
A loopful of culture is spread thinly on a slide and air-dried.
How is a smear prepared from solid culture?
A small colony is mixed with water on the slide before spreading.
What is the staining time for methylene blue?
1–2 minutes.
What is the staining time for crystal violet?
20–60 seconds.
What is the staining time for carbol fuchsin?
15–30 seconds.
How should excess stain be removed?
Gently rinse with tap water, holding the slide parallel to the stream.
How should the slide be dried after staining?
Blot with bibulous paper (do not wipe).
What microscope objective is used for final observation?
Oil immersion (100X).
What color do bacterial cells appear after simple staining?
Depends on the dye (e.g., purple with crystal violet, blue with methylene blue).
What shape are cocci bacteria?
Spherical.
What shape are bacilli bacteria?
Rod-shaped.
What shape are spirilla bacteria?
Spiral-shaped.
What does “staphylococci” arrangement mean?
Clusters of spherical bacteria.
What does “streptobacilli” arrangement mean?
Chains of rod-shaped bacteria.
Why might a smear appear too dark under the microscope?
Over-application of bacteria or stain.
What happens if a slide is overheated during fixation?
Cells may distort or rupture.
What is the background color in negative staining?
Dark (due to acidic dyes like nigrosin), while cells remain unstained.
Why do some cells show deeper-stained granules?
Due to higher nucleic acid concentration in certain regions.
What equipment is needed for simple staining?
Glass slides, inoculating loop, Bunsen burner, staining tray, microscope, lens paper.
What is the role of a mordant in staining?
Enhances dye binding (e.g., iodine in Gram staining).
What is a counterstain?
A secondary dye (e.g., safranin) used in differential staining.
What is the difference between basic and acidic dyes?
Basic dyes stain cells (positive charge), while acidic dyes stain the background (negative charge)
What is the purpose of immersion oil?
Reduces light refraction, improving resolution under 100X magnification.
How does simple staining differ from Gram staining?
Simple staining uses one dye, while Gram staining uses multiple dyes to classify bacteria.
What is the principle of Gram staining?
Based on cell wall composition (peptidoglycan thickness).
What color are Gram-positive bacteria after Gram staining?
Purple (retain crystal violet).
What color are Gram-negative bacteria after Gram staining?
Pink/red (take up safranin).
What is acid-fast staining used for?
To identify Mycobacterium (retains carbol fuchsin despite acid wash).
Why might bacteria not appear stained?
Insufficient staining time, old dye, or improper fixation.
What causes uneven staining?
Uneven smear thickness or incomplete washing.
Why do cells wash off during staining?
Inadequate heat fixation or thick smear.
How can over-decolorization affect Gram staining?
Gram-positive cells may appear Gram-negative.
What is the most common mistake in simple staining?
Applying too much bacterial culture, leading to clumping.
Is simple staining used in diagnostic labs?
Rarely; differential stains (Gram, AFB) are preferred for identification.
When is simple staining useful?
Quick morphology checks, teaching labs, or initial bacterial observation.
Can simple staining identify bacterial species?
No, it only reveals shape/arrangement, not species-specific traits.
What is the advantage of negative staining?
No heat fixation required, preserving delicate structures (e.g., capsules).
What is the main limitation of simple staining?
Cannot differentiate bacterial types (e.g., Gram-positive vs. Gram-negative).
Simple Staining 40 MCQs:
- What is the primary purpose of simple staining?
a) To differentiate Gram-positive and Gram-negative bacteria
b) To visualize bacterial morphology and arrangement
c) To identify bacterial capsules
d) To detect bacterial endospores - Which of the following is NOT a basic dye used in simple staining?
a) Methylene blue
b) Crystal violet
c) Nigrosin
d) Carbol fuchsin - Why do basic dyes adhere to bacterial cells?
a) Bacterial cells are positively charged
b) Bacterial cells are negatively charged
c) Basic dyes are hydrophobic
d) Basic dyes react with cell wall lipids - Which staining technique uses only one dye?
a) Gram staining
b) Acid-fast staining
c) Simple staining
d) Endospore staining - What type of staining colors the background instead of the cells?
a) Positive staining
b) Negative staining
c) Differential staining
d) Capsule staining
- What is the correct order of steps in simple staining?
a) Fixation → Staining → Smear preparation → Washing
b) Smear preparation → Fixation → Staining → Washing
c) Staining → Washing → Fixation → Smear preparation
d) Washing → Fixation → Smear preparation → Staining - Why is heat fixation used in simple staining?
a) To sterilize the slide
b) To kill bacteria and adhere them to the slide
c) To enhance dye penetration
d) To dissolve bacterial capsules - What happens if a slide is overheated during fixation?
a) Cells appear brighter
b) Cells may distort or rupture
c) Stain adheres better
d) Background becomes darker - How long should methylene blue be left on a smear?
a) 5–10 seconds
b) 1–2 minutes
c) 10–15 minutes
d) 30–60 seconds - Which microscope objective is used for final observation in simple staining?
a) 4X
b) 10X
c) 40X
d) 100X (oil immersion)
- Which dye is commonly used for negative staining?
a) Crystal violet
b) Methylene blue
c) Nigrosin
d) Safranin - What is the charge of acidic dyes?
a) Positive
b) Negative
c) Neutral
d) Variable - Which stain is NOT used in simple staining?
a) Methylene blue
b) Crystal violet
c) Carbol fuchsin
d) Iodine - What is the role of immersion oil in microscopy?
a) To sterilize the slide
b) To increase light refraction and resolution
c) To decolorize cells
d) To fix bacteria - Which dye is used for acid-fast staining?
a) Methylene blue
b) Crystal violet
c) Carbol fuchsin
d) Safranin
- What shape are cocci bacteria?
a) Rod-shaped
b) Spiral-shaped
c) Spherical
d) Comma-shaped - What does “streptobacilli” arrangement refer to?
a) Clusters of rods
b) Chains of rods
c) Pairs of spheres
d) Grape-like clusters - Which arrangement describes “staphylococci”?
a) Chains of cocci
b) Pairs of cocci
c) Clusters of cocci
d) Tetrads of cocci - What shape are spirilla bacteria?
a) Spherical
b) Rod-shaped
c) Spiral
d) Filamentous - Which of the following is NOT a bacterial arrangement?
a) Diplo-
b) Strepto-
c) Staphylo-
d) Flagello-
- Which staining method differentiates Gram-positive and Gram-negative bacteria?
a) Simple staining
b) Negative staining
c) Gram staining
d) Acid-fast staining - What is the primary stain in Gram staining?
a) Methylene blue
b) Crystal violet
c) Safranin
d) Nigrosin - Which bacteria retain crystal violet in Gram staining?
a) Gram-negative
b) Gram-positive
c) Acid-fast
d) Capsulated - What is the counterstain in Gram staining?
a) Methylene blue
b) Crystal violet
c) Safranin
d) Carbol fuchsin - Which staining technique is used for Mycobacterium?
a) Gram staining
b) Acid-fast staining
c) Simple staining
d) Negative staining
- Why might bacteria not appear stained after simple staining?
a) Overheating
b) Insufficient staining time
c) Using too much water
d) All of the above - What causes uneven staining?
a) Thick smear
b) Incomplete washing
c) Old dye
d) All of the above - Why do cells wash off during staining?
a) Inadequate fixation
b) Excessive rinsing
c) Thin smear
d) None of the above - What happens if decolorization is excessive in Gram staining?
a) Gram-positive cells appear Gram-negative
b) Gram-negative cells appear Gram-positive
c) No effect
d) Cells become colorless - What is the most common mistake in simple staining?
a) Using too little stain
b) Applying too much bacterial culture
c) Skipping fixation
d) Using acidic dyes
- Is simple staining used in diagnostic labs?
a) Yes, as the primary method
b) No, differential stains are preferred
c) Only for fungal identification
d) Only for viral cultures - When is negative staining useful?
a) To visualize capsules
b) To identify Gram-positive bacteria
c) To detect endospores
d) To study flagella - What is the main limitation of simple staining?
a) Cannot differentiate bacterial types
b) Requires expensive dyes
c) Takes too long
d) Only works on viruses - Which staining technique is the quickest?
a) Gram staining
b) Acid-fast staining
c) Simple staining
d) Endospore staining - What is the advantage of simple staining?
a) Identifies bacterial species
b) Shows cell wall structure
c) Quick and easy morphology check
d) Detects antibiotic resistance
- Which bacterial component attracts basic dyes in simple staining?
a) Lipids
b) Nucleic acids
c) Polysaccharides
d) Water - What is the purpose of blotting the slide after staining?
a) To remove excess water
b) To enhance dye penetration
c) To sterilize the slide
d) To decolorize cells - Which staining method does NOT require heat fixation?
a) Simple staining
b) Gram staining
c) Negative staining
d) Acid-fast staining - What color do Gram-negative bacteria appear after Gram staining?
a) Purple
b) Pink/red
c) Blue
d) Green - Which staining technique is used for endospores?
a) Simple staining
b) Gram staining
c) Acid-fast staining
d) Schaeffer-Fulton staining
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