AP-Micro Bacterial Classification 3 — Questions and Answers
Question 1: Which of the following cell arrangements describes bacteria that divide in one plane and remain attached in chains?
- Sarcinae
- Tetrads
- Streptococci (Correct answer)
- Staphylococci
Correct answer: Streptococci
Streptococci divide in a single plane and remain attached, forming chains of spherical cells.
Question 2: Proteobacteria are subdivided into classes (Alpha, Beta, Gamma, etc.) based on:
- Optimal growth temperature
- 16S rRNA sequence similarity (Correct answer)
- Gram stain result
- Spore-forming ability
Correct answer: 16S rRNA sequence similarity
Classes within Proteobacteria are defined by 16S rRNA phylogenetic analysis reflecting evolutionary relatedness.
Question 3: Which genus forms endospores that allow survival in boiling water for extended periods?
- Staphylococcus
- Mycoplasma
- Clostridium (Correct answer)
- Neisseria
Correct answer: Clostridium
Clostridium (and Bacillus) endospores are highly heat-resistant structures that can survive boiling temperatures.
Question 4: A Gram-negative diplococcus isolated from a urethral swab is most likely which organism?
- Streptococcus pneumoniae
- Staphylococcus epidermidis
- Neisseria gonorrhoeae (Correct answer)
- Bacillus cereus
Correct answer: Neisseria gonorrhoeae
Neisseria gonorrhoeae is a Gram-negative diplococcus and the causative agent of gonorrhea.
Question 5: What is the primary basis for distinguishing Streptococcus species from one another in clinical labs?
- Gram stain reaction
- Hemolysis pattern on blood agar (Correct answer)
- Cell shape
- Motility
Correct answer: Hemolysis pattern on blood agar
Streptococci are categorized as alpha-, beta-, or gamma-hemolytic based on how they lyse red blood cells on blood agar.
Question 6: Which of the following bacteria is an example of a spirochete?
- Campylobacter jejuni
- Treponema pallidum (Correct answer)
- Vibrio cholerae
- Helicobacter pylori
Correct answer: Treponema pallidum
Treponema pallidum, the causative agent of syphilis, is a spirochete with a characteristic corkscrew morphology.
Question 7: Facultative anaerobes are best described as organisms that:
- Require oxygen for growth
- Are killed by oxygen
- Can grow with or without oxygen (Correct answer)
- Grow only at very low oxygen levels
Correct answer: Can grow with or without oxygen
Facultative anaerobes can perform aerobic respiration when oxygen is available but switch to fermentation or anaerobic respiration without it.
AP-Micro Bacterial Classification 3
Which of the following cell arrangements describes bacteria that divide in one plane and remain attached in chains?