This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: Coprococcus occurs in human feces and uses carbohydrates as a major source of carbon and energy.
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