This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “World of Bacteria I – Mycoplasmas”.
1. The smallest cells of mycoplasmas are about ___________ in diameter.
a) 1 micrometre
b) 0.3 micrometre
c) 5 micrometre
d) 1 metre
Explanation: The smallest cells of Mycoplasmas are about 0.3 micrometre in diameter and the plasticity of these cells allow them to pass even through bacteriological filters.
2. Penicillin causes inhibition of Mycoplasmas.
Explanation: Because of the lack of a cell wall, mycoplasmas are not inhibited by even high levels of penicillin; however, they can be inhibited by antibiotics that affect protein synthesis, such as tetracyclines or chloramphenicol.
3. Mycoplasmas can be cultivated in vitro on nonliving media as _____________
a) facultative aerobes
b) obligate aerobes
c) facultative anaerobes
Explanation: Mycoplasmas can be cultivated in vitro on nonliving media (of rich composition) as facultative anaerobes or obligate anaerobes.
4. The colonies of Mycoplasmas in agar plate can be observed by means of a _______________
a) low-power microscope
b) high-power microscope
c) phase contrast microscopy
d) bright-field microscopy
Explanation: Colonies on agar plate are usually tiny and require observation by means of a low-power microscope. The colonies are embedded in the agar surface and usually have a characteristic fried-egg appearance.
5. What type of colonies are formed by Mycoplasmas on the agar plate?
c) lawn formation
Explanation: The colonies are embedded in the agar surface and usually have a characteristic fried-egg appearance. The colonies are usually very tiny.
6. The mycoplasmas require which of the following substance for growth?
Explanation: The Mycoplasmas require cholesterol for growth and are parasites of the mucous membranes and joints of humans or animals.
7. Which of the following family of bacteria are pathogenic for citrus and other plants?
Explanation: The organisms of Spiroplasmataceae are pathogenic for citrus and other plants. They can be isolated from plant fluids and plant surfaces and from arthropods that feed on plants.
8. Lyticum flagellatum is an endosymbiont carried by certain strains of __________________
Explanation: Lyticum flagellatum is an endosymbiont carried by certain strains of the protozoan Paramecium tetraurelia.
9. L.flagellatum performs the function of synthesizing _______________
c) organic acids
d) folic acid and toxins
Explanation: One function of L.flagellatum is to synthesize the vitamin folic acid for its host; another function is to produce a toxin that is liberated into the culture medium.
10. Mycoplasmas cannot give rise to walled bacterial form like L-phase variants.
Explanation: L-phase variants are derived from walled bacteria and can usually revert to the normal walled bacterial form, whereas mycoplasmas do not give rise to walled forms.
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