Flagella Stain 50 FAQs and 30 MCQs
Flagella Stain 50 FAQs
What are bacterial flagella?
Filamentous structures for motility, made of flagellin protein.
What is the diameter and length of bacterial flagella?
~12-30 nm in diameter, 5-16 µm in length.
What are the four types of flagellar arrangements?
Monotrichous, amphitrichous, lophotrichous, peritrichous.
Give an example of a monotrichous bacterium.
Vibrio cholerae.
Which bacteria have peritrichous flagella?
Salmonella Typhi.
What are the three parts of a flagellum?
Filament, hook, basal body.
What is the function of flagella besides motility?
Sensation, adhesion, signal transduction, virulence.
Why is flagella staining necessary?
Flagella are too thin to be seen under a normal microscope.
What is the objective of flagella staining?
To visualize flagella for bacterial identification.
What staining technique is used for flagella?
Wet mount technique with a mordant.
What is the role of a mordant in flagella staining?
Helps stain adhere in layers to flagella for visibility.
Why can’t Gram stain visualize flagella?
Flagella are too thin for ordinary stains.
What is the Ryu flagella stain method?
Uses crystal violet, tannic acid, and phenol to precipitate stain around flagella.
What medium is best for growing bacteria before flagella staining?
Blood agar (16-24 hours at room temp).
Why should cultures not be too old for flagella staining?
Older cultures may lose flagella.
How do you prepare a wet mount for flagella staining?
Place a water drop on a slide, let motile cells swim in, and cover with a coverslip.
Why should you avoid agitating the loop in the water droplet?
It may shear off flagella.
How long should you wait before applying the flagella stain?
5-10 minutes for cells to adhere.
What is the optimal staining time for Ryu’s method?
4 minutes (adjustable between 2-8 minutes).
Should you heat-fix the slide before staining?
No, air-dry only (heat fixing destroys flagella).
How do you apply the stain in the wet mount technique?
Let it flow under the coverslip via capillary action.
At what magnification should you check for motility first?
40× to 50×.
What magnification is used to observe stained flagella?
100× (oil immersion).
Where should you focus to see flagella clearly?
On cells attached to the coverslip, not the slide.
What are the main components of Hardy’s Flagella Stain?
Crystal violet, tannic acid, aluminum potassium sulfate, phenol.
Why is phenol used in flagella stain?
Acts as an antifungal agent.
What safety precautions are needed when handling flagella stain?
Avoid skin/eye contact, use a fume hood, wear PPE.
What happens if the stain is expired?
Do not use; may give unreliable results.
How should flagella stain be stored?
2-30°C, protected from light.
What is the shelf life of flagella stain?
Check expiration date; typically stable if stored properly.
What should you observe in a successful flagella stain?
Purple-stained bacteria with visible flagella.
What does peritrichous flagella arrangement look like?
Flagella all over the bacterial surface.
What does lophotrichous mean?
Tufts of flagella at one or both poles.
What are possible errors in flagella staining?
Over-staining (precipitate), under-staining (faint flagella), shearing flagella.
Why might flagella not be visible after staining?
Old culture, improper technique, or non-motile bacteria.
How does temperature affect flagella visibility?
Some bacteria (e.g., Pseudomonas) show better flagellation at 25°C.
What bacteria are used as QC for flagella stain?
Proteus vulgaris (peritrichous), Pseudomonas aeruginosa (monotrichous).
What is a false-negative result in flagella staining?
Motile bacteria appear non-motile due to poor technique.
How can you improve flagella staining results?
Use fresh cultures, avoid agitation, optimize staining time.
What if the stain precipitates on the slide?
Reduce staining time.
What if flagella are faintly stained?
Increase staining time (up to 8 minutes).
Why is blood agar preferred for flagella staining?
Minimal fermentable content reduces flagella loss.
Can you use broth cultures for flagella staining?
Not ideal; agar colonies are preferred.
How often should you QC flagella stain?
Weekly with positive/negative controls.
How is flagella staining useful in taxonomy?
Helps differentiate motile species based on flagellar arrangement.
Can flagella staining detect anaerobic bacteria?
Yes, with modified techniques.
Why is flagella staining not an entry-level technique?
Requires experience to avoid artifacts.
How does motility contribute to bacterial virulence?
Helps in tissue invasion and biofilm formation.
What alternatives exist for flagella visualization?
Electron microscopy (more precise but complex).
What is the historical significance of Ryu’s stain?
Developed in 1937, still widely used for its simplicity.
Flagella Stain 30 MCQs:
- What is the primary protein component of bacterial flagella?
a) Keratin
b) Flagellin
c) Actin
d) Tubulin - Which of the following bacteria has monotrichous flagella?
a) Salmonella Typhi
b) Vibrio cholerae
c) Escherichia coli
d) Spirillum - Peritrichous flagella refer to:
a) A single flagellum at one pole
b) Flagella at both poles
c) Tufts of flagella at one end
d) Flagella distributed all over the cell - The basal body of flagella is anchored to the:
a) Cell wall
b) Cytoplasmic membrane
c) Nucleoid
d) Ribosomes
- Why is a mordant used in flagella staining?
a) To kill the bacteria
b) To thicken flagella for visibility
c) To decolorize the cells
d) To fix the flagella - Which stain is commonly used in Ryu’s flagella staining method?
a) Gram’s crystal violet
b) Methylene blue
c) Carbol fuchsin
d) Phenol-based crystal violet - Flagella staining is a type of:
a) Simple staining
b) Negative staining
c) Wet mount staining
d) Acid-fast staining - What is the purpose of phenol in flagella stain?
a) To act as a mordant
b) To prevent fungal contamination
c) To fix the cells
d) To enhance motility
- Before staining, bacteria should be grown on:
a) MacConkey agar
b) Blood agar
c) Nutrient broth
d) Chocolate agar - Why should you avoid heat-fixing in flagella staining?
a) It destroys flagella
b) It inhibits motility
c) It prevents stain adherence
d) It degrades the mordant - How long should the stain remain on the slide in Ryu’s method?
a) 30 seconds
b) 2–8 minutes
c) 15 minutes
d) 1 hour - Capillary action is used to:
a) Mix stain with bacterial suspension
b) Heat-fix the slide
c) Wash off excess stain
d) Observe motility
- Under oil immersion, flagella appear:
a) Red
b) Purple
c) Green
d) Colorless - Excessive staining time may cause:
a) Faint flagella
b) Crystal violet precipitate
c) Cell lysis
d) Loss of motility - Which bacterium is a QC positive control for peritrichous flagella?
a) Pseudomonas aeruginosa
b) Klebsiella pneumoniae
c) Proteus vulgaris
d) Escherichia coli - Flagella are best observed in which growth phase?
a) Lag phase
b) Log phase
c) Stationary phase
d) Death phase
- Flagella staining is not recommended for beginners because:
a) It requires toxic reagents
b) Results are highly technique-dependent
c) It uses expensive equipment
d) It only works for Gram-positive bacteria - Which component of flagella stain is harmful if inhaled?
a) Tannic acid
b) Phenol
c) Aluminum sulfate
d) Distilled water - Storage of flagella stain requires protection from:
a) Light
b) Oxygen
c) Cold temperatures
d) Humidity - A false-negative result in flagella staining may occur due to:
a) Over-staining
b) Using fresh cultures
c) Shearing flagella during preparation
d) Proper air-drying
- Which microscope is better than light microscopy for flagella visualization?
a) Phase-contrast
b) Electron microscope
c) Dark-field
d) Fluorescence - Motility in bacteria aids in:
a) Spore formation
b) Virulence and tissue invasion
c) Antibiotic resistance
d) Capsule production - Ryu’s stain was developed in:
a) 1857
b) 1937
c) 1982
d) 2005 - Which temperature is ideal for flagella production in Pseudomonas?
a) 37°C
b) 25°C
c) 42°C
d) 15°C
- Flagella staining can be used to identify anaerobic bacteria.
a) True
b) False - Gram staining is sufficient to visualize flagella.
a) True
b) False - A coverslip is optional in wet mount flagella staining.
a) True
b) False - Flagella staining is a confirmatory test for bacterial motility.
a) True
b) False
- After staining, you observe clumps of bacteria but no flagella. What went wrong?
a) Over-mixing the sample
b) Using log-phase culture
c) Proper air-drying
d) Optimal stain time - Your flagella stain shows excessive precipitate. How do you fix this?
a) Increase staining time
b) Reduce staining time
c) Use a stronger mordant
d) Heat-fix the slide
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