Morphological classification of bacteria MCQs With Answer is a focused review designed for B. Pharm students to master bacterial shapes, arrangements, staining correlations and diagnostic features. This concise, keyword-rich introduction covers coccus, bacillus, vibrio, spirillum, spirochete, coccobacilli, pleomorphism, endospore morphology, and arrangement terms like diplococci, streptococci and staphylococci. Emphasis on Gram staining, flagellar patterns, axial filaments, and microscopic techniques helps build practical identification skills. These MCQs are ideal for exam prep, practicals and quick revision, reinforcing core concepts and clinical relevance. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. Which bacterial shape is spherical?
- Rod
- Spiral
- Comma
- Coccus
Correct Answer: Coccus
Q2. Which term describes bacteria arranged in chains?
- Staphylococci
- Streptococci
- Diplococci
- Sarcina
Correct Answer: Streptococci
Q3. A short oval-shaped bacterium that is intermediate between cocci and bacilli is called:
- Spirochete
- Coccobacillus
- Vibrio
- Filamentous rod
Correct Answer: Coccobacillus
Q4. Which structure gives spirochetes their characteristic motility?
- Periplasmic flagella (axial filaments)
- Capsule
- Pili
- Endospore
Correct Answer: Periplasmic flagella (axial filaments)
Q5. Which bacterial genus shows branching filamentous morphology similar to fungi?
- Staphylococcus
- Actinomyces
- Vibrio
- Neisseria
Correct Answer: Actinomyces
Q6. Which arrangement is typical for Staphylococcus aureus?
- Chains
- Pairs
- Clusters
- Tetrads
Correct Answer: Clusters
Q7. Which of the following describes a comma-shaped bacterium?
- Vibrio
- Spirochete
- Coccus
- Budding rod
Correct Answer: Vibrio
Q8. Which microscope technique enhances contrast without staining, useful for live bacterial morphology?
- Electron microscopy
- Phase contrast microscopy
- Gram staining
- Acid-fast staining
Correct Answer: Phase contrast microscopy
Q9. Which flagellar arrangement has a single flagellum at one pole?
- Peritrichous
- Monotrichous
- Lophotrichous
- Amphitrichous
Correct Answer: Monotrichous
Q10. Which bacteria are typically rod-shaped and form endospores?
- Bacillus and Clostridium
- Neisseria and Moraxella
- Streptococcus and Enterococcus
- Mycoplasma and Ureaplasma
Correct Answer: Bacillus and Clostridium
Q11. Tetrad arrangement refers to bacteria grouped in:
- Two cells
- Four cells in a square
- Chains of many cells
- Irregular clusters
Correct Answer: Four cells in a square
Q12. Which of the following is a spirochete genus?
- Treponema
- Salmonella
- Staphylococcus
- Bordetella
Correct Answer: Treponema
Q13. Which morphological term describes bacteria that vary in shape and size under different conditions?
- Pleiomorphism
- Monomorphism
- Filamentation
- Palissading
Correct Answer: Pleiomorphism
Q14. Palisade arrangement is characteristic of which genus due to snapping division?
- Corynebacterium
- Escherichia
- Clostridium
- Neisseria
Correct Answer: Corynebacterium
Q15. Which method is best for visualizing bacterial capsules?
- Gram staining
- Negative staining (e.g., India ink)
- Endospore stain
- Acid-fast stain
Correct Answer: Negative staining (e.g., India ink)
Q16. Which arrangement describes groups of eight spherical cells forming a cube?
- Streptococci
- Sarcina
- Diplococci
- Staphylococci
Correct Answer: Sarcina
Q17. Which morphological feature differentiates spirillum from spirochete?
- Spirillum are rigid and have external flagella; spirochetes are flexible with axial filaments
- Spirochetes are shorter than spirilla
- Spirilla are Gram-positive only
- Spirochetes form endospores
Correct Answer: Spirillum are rigid and have external flagella; spirochetes are flexible with axial filaments
Q18. Which of these bacteria typically appears as diplococci?
- Streptococcus pyogenes
- Neisseria gonorrhoeae
- Escherichia coli
- Bacillus subtilis
Correct Answer: Neisseria gonorrhoeae
Q19. Which microscopy provides the highest resolution to observe bacterial ultrastructure?
- Bright-field light microscopy
- Electron microscopy
- Phase contrast microscopy
- Fluorescence microscopy
Correct Answer: Electron microscopy
Q20. Pleomorphic bacteria often lack a rigid cell wall; which genus exemplifies this?
- Mycoplasma
- Pseudomonas
- Staphylococcus
- Clostridium
Correct Answer: Mycoplasma
Q21. Which bacterial shape is most commonly associated with motility by flagella?
- Coccus (spherical) — rarely flagellated
- Bacillus (rod) — commonly flagellated
- Sarcina — highly motile
- Tetrad — peritrichous flagella
Correct Answer: Bacillus (rod) — commonly flagellated
Q22. Which morphological change is commonly observed during starvation or stress?
- Increased flagellar number
- Formation of spores or smaller pleomorphic forms
- Immediate lysis of all cells
- Conversion to multicellular eukaryotes
Correct Answer: Formation of spores or smaller pleomorphic forms
Q23. Which of the following is an example of a curvature rod bacterium associated with gastrointestinal disease?
- Vibrio cholerae
- Streptococcus pneumoniae
- Bacillus anthracis
- Mycobacterium tuberculosis
Correct Answer: Vibrio cholerae
Q24. Filamentous bacteria in soil that produce branching filaments and aerial hyphae are often from which group?
- Enterobacteriaceae
- Actinomycetes (Streptomyces)
- Neisseriaceae
- Clostridia
Correct Answer: Actinomycetes (Streptomyces)
Q25. Which bacterial structure is most directly related to determining Gram reaction and cell shape?
- Capsule
- Cell wall (peptidoglycan layer)
- Pilus
- Endospore
Correct Answer: Cell wall (peptidoglycan layer)
Q26. Which staining technique distinguishes bacteria with high mycolic acid content in the cell wall?
- Gram stain
- Acid-fast stain
- Endospore stain
- Negative stain
Correct Answer: Acid-fast stain
Q27. Which term describes bacteria with flagella distributed over the entire cell surface?
- Monotrichous
- Lophotrichous
- Peritrichous
- Amphitrichous
Correct Answer: Peritrichous
Q28. Which morphological feature can be used to identify Bacillus anthracis microscopically?
- Club-shaped rods in Chinese letter arrangement
- Large, boxcar-shaped rods often with central endospores
- Gram-negative cocci in pairs
- Curved rods with polar flagella
Correct Answer: Large, boxcar-shaped rods often with central endospores
Q29. Which genus is known for coccobacillary shape and is a common cause of otitis and respiratory infections?
- Haemophilus
- Bacillus
- Clostridium
- Streptomyces
Correct Answer: Haemophilus
Q30. Which of the following best explains why Gram staining sometimes fails to reflect exact morphology?
- Gram stain uses electron beams that alter shape
- Morphology is independent of staining and never affected
- Cell wall damage, age of culture or improper technique can alter staining and apparent morphology
- Only cocci can be visualized by Gram stain
Correct Answer: Cell wall damage, age of culture or improper technique can alter staining and apparent morphology
Q31. Which bacterial group is characteristically slender, pleomorphic and may resist standard Gram staining due to lack of peptidoglycan?
- Mycoplasma
- Pseudomonas
- Enterococcus
- Bacillus
Correct Answer: Mycoplasma
Q32. Which arrangement is commonly seen in Streptococcus pneumoniae?
- Clusters
- Pairs (diplococci)
- Tetrads
- Filamentous chains
Correct Answer: Pairs (diplococci)
Q33. Which morphological form is associated with bacteria that reproduce by budding rather than binary fission?
- Hyphal or budding rods like Hyphomicrobium
- Classic cocci produced by binary fission only
- Strict spirochetes forming endospores
- All Gram-negative rods
Correct Answer: Hyphal or budding rods like Hyphomicrobium
Q34. Which microscopic technique is most useful for observing living unstained bacteria motility and morphology?
- Bright-field with heat-fixed smear
- Phase contrast or dark-field microscopy
- Standard Gram stain under oil immersion
- Acid-fast stained smear
Correct Answer: Phase contrast or dark-field microscopy
Q35. Which of the following arrangements describes bacteria in V-shapes or Chinese letters?
- Palisade arrangement from snapping division
- Sarcina cube formation
- Peritrichous motility pattern
- Endospore localization
Correct Answer: Palisade arrangement from snapping division
Q36. Which genus is a Gram-negative curved rod often associated with gastric colonization?
- Helicobacter
- Staphylococcus
- Bacillus
- Clostridium
Correct Answer: Helicobacter
Q37. Bacterial endospores are best described as:
- Reproductive structures released to form new bacteria
- Highly resistant dormant structures formed within vegetative cells
- Surface appendages for attachment
- Only present in Gram-negative cocci
Correct Answer: Highly resistant dormant structures formed within vegetative cells
Q38. Which arrangement term applies to bacteria forming grape-like clusters?
- Streptococci
- Staphylococci
- Diplococci
- Tetrads
Correct Answer: Staphylococci
Q39. Which of the following is true about morphology-based bacterial classification?
- Morphology alone is sufficient for definitive species identification
- Morphology aids preliminary identification but must be combined with biochemical and molecular tests
- All rods are Gram-positive
- Shape never changes with environment
Correct Answer: Morphology aids preliminary identification but must be combined with biochemical and molecular tests
Q40. Which form describes bacteria with variable shapes often seen in Corynebacterium species?
- Club-shaped rods (palisades)
- Spherical chains
- Spiral motility rods
- Strictly filamentous hyphae
Correct Answer: Club-shaped rods (palisades)
Q41. Which descriptor fits bacteria like Vibrio vulnificus?
- Gram-positive cocci in clusters
- Curved Gram-negative rods with polar flagella
- Filamentous Gram-positive branching rods
- Acid-fast bacilli
Correct Answer: Curved Gram-negative rods with polar flagella
Q42. Which staining method is used specifically to detect bacterial endospores?
- Gram stain
- Endospore (Schaeffer-Fulton) stain
- Capsule stain
- Acid-fast stain
Correct Answer: Endospore (Schaeffer-Fulton) stain
Q43. A bacterium that is curved and rod-shaped with a single polar flagellum at one end is termed:
- Peritrichous rod
- Monotrichous curved rod
- Coccobacillus with multiple flagella
- Sarcina
Correct Answer: Monotrichous curved rod
Q44. Which morphological trait is typical of Neisseria species?
- Gram-negative diplococci
- Gram-positive branching filaments
- Endospore-forming rods
- Helical spirochetes
Correct Answer: Gram-negative diplococci
Q45. Which of the following statements about coccobacilli is correct?
- They are long, filamentous bacteria only found in soil
- They are intermediate in shape between cocci and bacilli and can complicate microscopic identification
- They always form spores
- They are only Gram-positive
Correct Answer: They are intermediate in shape between cocci and bacilli and can complicate microscopic identification
Q46. Which bacterial arrangement is characterized by cells dividing in multiple planes producing irregular clusters?
- Streptococcus
- Staphylococcus
- Diplococcus
- Sarcina
Correct Answer: Staphylococcus
Q47. Which technique is preferred to observe external flagella arrangement on bacteria?
- Negative staining with India ink
- Special flagella stain (e.g., Leifson’s) or electron microscopy
- Endospore staining
- Acid-fast staining
Correct Answer: Special flagella stain (e.g., Leifson’s) or electron microscopy
Q48. Which of the following genera is typically described as slender, pleomorphic, and acid-fast variable due to mycolic acids?
- Mycobacterium
- Escherichia
- Streptococcus
- Vibrio
Correct Answer: Mycobacterium
Q49. Which of these morphological features is commonly used in initial laboratory identification of bacteria?
- Growth on selective media only
- Cell shape, arrangement and Gram reaction observed microscopically
- Only molecular sequencing results
- Presence of mitochondria
Correct Answer: Cell shape, arrangement and Gram reaction observed microscopically
Q50. Why is morphological classification still taught despite molecular taxonomy advances?
- Morphology is obsolete and never used in clinics
- It provides rapid, low-cost preliminary identification and guides further testing
- It replaces all biochemical and molecular methods
- It only applies to viruses
Correct Answer: It provides rapid, low-cost preliminary identification and guides further testing
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