Microbiology Multiple Choice Questions on “World of Bacteria II – Gram – Positive Cocci”.
1. The cocci belonging to the family Dienococcaceae occur mainly in _______________
A. tetrads
B. diplococci
C. streptococci
D. staphylococci
Answer: A
Clarification: The cocci belonging to the family Deinococcaceae occurs mainly in tetrads or cubical packets.
2. The organisms belonging to the genus Deinococcus forms colonies of which color?
A. colourless
B. blue
C. red
D. violet
Answer: C
Clarification: The family Deinococcaceae contains a single genus Deinococcus which forms red colonies.
3. The family Micrococcaceae do not exhibit any unusual resistance to gamma and ultraviolet radiation.
A. True
B. False
Answer: A
Clarification: The family Micrococcaceae do not exhibit any unusual resistance to gamma and ultraviolet radiation. But the organisms belonging to family Deinococcaceae have an unusually high resistance to gamma and ultraviolet radiations.
4. Among the following which is positive for coagulase test?
A. Staphylococcus aureus
B. Staphylococcus epidermidis
C. Staphylococcus saprophyticus
D. E.coli
Answer: A
Clarification: Staphylococcus aureus is positive for coagulase test which is a test for the ability of the bacteria to cause blood plasma to clot.
5. Streptococcus are catalase-positive.
A. True
B. False
Answer: B
Clarification: Streptococcus are catalase-negative. The organisms are homofermentative i.e., the predominant end product of sugar fermentation is lactic acid.
6. Which of the following species of streptococci belongs to Lancefield group N?
A. S.pyogenes
B. S.mutans
C. S.pneumoniae
D. S.cremoris
Answer: D
Clarification: The streptococci are divided into categories known as the Lancefield groups based on differences in their cell-wall polysaccharides. S.cremoris belong to Lancefield group N and are harmless contaminants of milk and dairy products.
7. S.pneumoniae produces which of the following type of colonies?
A. alpha-haemolytic
B. beta-haemolytic
C. non-haemolytic
D. alpha-, beta-haemolytic
Answer: A
Clarification: S.pneumoniae are alpha-haemolytic i.e. colonies are surrounded by a cloudy, colorless or greenish zone of partially lysed erythrocytes.
8. Which of the following is the causative agent of dental caries?
A. S.pneumoniae
B. S.pyogenes
C. S.mutans
D. S.faecalis
Answer: C
Clarification: S.mutans inhabits the human oral cavity and is the major causative agent of dental caries.
9. Which of the following genus of species occurs in human feces?
A. Peptococcus
B. Coprococcus
C. Sarcina
D. Ruminococcus
Answer: B
Clarification: Coprococcus occurs in human feces and uses carbohydrates as a major source of carbon and energy.
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