Interview MCQ Set 1
1. The nucleic scid core of phages is covered by a protein coat known as _______________
c) outer envelope
d) nuclear membrane
Answer: b [Reason:] All phages have a nucleic acid core covered by a protein coat or capsid.The capsid is made up of morphological subunits called capsomeres.
2. The most complex type of bacterial virus has which of the following morphological features?
a) hexagonal head and tail fibres
b) no contractile sheath
c) hexagonal head but no tail
d) hexagonal head,rigid tail with contractile sheath
Answer: d [Reason:] The most complex type has a hexagonal head, a rigid tail with a contractile sheath, and tail fibres.
3. Which of the following is true for the bacteriophage MV-L2 ?
a) head is made up of large capsomeres
b) head is made up of small capsomeres
c) no contractile sheath is present
d) filamentous form
Answer: d [Reason:] Bacteriophage MV-L2 has a filamentous form.This type is found in some plant viruses.
4. Pleomorphic viruses possess double-stranded DNA.
Answer: a [Reason:] Pleomorphic viruses were recently discovered to have a lipid-containing envelope, have no detectable capsid, and possess double-stranded DNA (ds-DNA).
5. What is the shape of helical phages?
a) regular solids
Answer: c [Reason:] Helical phages are rod-shaped whereas cubical phages are regular solids or more specifically polyhedra.
6. Which of the following are said to have binal symmetry?
Answer: b [Reason:] T-even coliphages such as T2,T4, and T6, are said to have binal symmetry because each virion has both an icosahedral head and a hollow helical tail.
7. The DNA of phage lambda is circular both in the virion and in the host cell.
Answer: b [Reason:] The DNA of phage lambda is linear in the virion,but on entering the host cell the cohesive ends join to form a circle.
8. Which of the following is a family of lambda phage viruses?
Answer: c [Reason:]Styloviridae is a family of lambda phage viruses that are non-enveloped and has dsDNA.
9. Which of the following coliphage has tadpole shape?
Answer: d [Reason:] T3 and T7 have tadpole shapes and the tails are very short.All others have polyhedra heads and long tails.
10. Which of the following are filamentous phage of E.coli?
c) f1 and fd
d) T3 and T7
Answer: c [Reason:] Filamentous phages of E.coli include f1 and fd bacteriophages.They all have circular single-stranded DNA.
Interview MCQ Set 2
1. The smallest cells of mycoplasmas are about ___________ in diameter.
a) 1 micrometre
b) 0.3 micrometre
c) 5 micrometre
d) 1 metre
Answer: b [Reason:] The smallest cells of Mycoplasmas are about 0.3 micrometre in diametre and the plasticity of these cells allow them to pass even through bacteriological filters.
2. Penicillin causes inhibition of Mycoplasmas.
Answer: b [Reason:] 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
Answer: c [Reason:] 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
Answer: a [Reason:] 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 agar plate?
c) lawn formation
Answer: d [Reason:] 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?
Answer: c [Reason:] 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?
Answer: c [Reason:] 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 __________________
Answer: d [Reason:] 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
Answer: d [Reason:] 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.
Answer: a [Reason:] 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.
Interview MCQ Set 3
1. Ammonia oxidizers and nitrite oxidizers are ________________________
a) Gram-negative chemolithotrophs
b) Gram-positive chemolithotrophs
c) Gram-negative photolithotrophs
d) Gram-positive photolithotrophs
Answer: a [Reason:] Oxidation of ammonia to nitrite by ammonia-oxidizing bacteria and oxidation of nitrite to nitrate by nitrite-oxidizing bacteria, are both Gram-negative chemolithotrophs.
2. Alanine gives pyruvic acid on deamination.
Answer: a [Reason:] The process of removal of the amino group from amino acids is known as deamination. Alanine in presence of alanine deaminase gives pyruvic acid and ammonia as its deamination reaction products.
3. How much time does nitrifying bacteria requires to grow at an incubation of 250 to 300 C?
a) 1 day
b) 2-3 days
c) 15 days
d) 1 to 4 months
Answer: d [Reason:] For growth of nitrifying bacteria a relatively large inoculum is used, and incubation is in the dark at 250 to 300 C for a period of 1 to 4 months.
4. Nitrosococcus nitrosus is a nitrite-oxidizing bacteria.
Answer: b [Reason:] Nitrosococcus nitrosus is a type of ammonia-oxidizing bacteria.They usually have an extensive membrane system within their cytoplasm and frequently forms cysts and zooglea.
5. Which among the following is not an ammonia-oxidizing bacteria?
a) Nitrosomonas europaea
b) Nitrosovibrio tenuis
c) Nitrospina gracilis
d) Nitrosococcus oceanus
Answer: c [Reason:] Nitrospina gracilis is a nitrite-oxidizing bacteria.They are involved in the oxidation of nitrite to nitrate.
6. Agrobacterium is involved in which of the following processes?
c) Reduction of nitrate to ammonia
Answer: d [Reason:] The transformation of nitrates to gaseous nitrogen is known as denitrification. Species of several bacteria like Agrobacterium, Bacillus, Pseudomonas etc are involved in this process.
7. Which of the following conditions decreases the level of denitrification?
a) Abundance of organic matter
b) Acidic pH
c) Elevated temperatures
d) Availability of oxygen
Answer: b [Reason:] The process of denitrification is enhanced in soils by the presence of abundance of organic matter, by elevated temperatures, by neutral or alkaline pH.Availability of oxygen has a dual effect on denitrification.
8. Which of the following are not the features of component II of nitrogenase enzyme complex?
a) component II is nitrogenase reductase
b) component II is known as the MoFe protein
c) contains sulfur
d) not active without component I
Answer: b [Reason:] Component II of nitrogenase enzyme complex is nitrogenase reductase.It is a smaller molecule and is designated the Fe protein. Both molecules contain sulfur and neither is active without the other.
9. Which of the following is a symbiotic nitrogen fixing bacteria?
a) Rhizobium trifolii
b) Clostridium pasteurianum
c) Azotobacter sp.
d) Escherichia coli
Answer: a [Reason:] Symbiotic nitrogen fixation is accomplished by bacteria of the genus Rhizobium in association with legumes like Rhizobium trifolii.
Interview MCQ Set 4
1. Which of the following Nonspore forming Gram-positive rods show negative result for catalase test?
Answer: a [Reason:] Lactobacillus which are strictly fermentative organisms show negative result for catalase test.
2. Which of the following is a characteristic of the genus Caryophanon?
a) anaerobic species
b) non-motile organism
c) disk-shaped cells
Answer: c [Reason:] Caryophanon is unusual as it is composed of large,disk-shaped cells arranged in trichomes.They are aerobic organisms and are motile by peritrichous flagella.
3. Which of the following genus of organisms causes meningitis in adults?
Answer: b [Reason:] The species L.monocytogenes of the genus Listeria is a parasite and causes meningitis in adults and prenatal or postnatal disease in infants.
4. Brocothrix is a facultatively anaerobic genus of species.
Answer: a [Reason:] Brocothrix are rods often occurring in long,kinked filaments and are facultatively anaerobic.
5. Volutin granules stain which colour with dilute methylene blue?
d) Reddish purple
Answer: d [Reason:] The cells of Corynebacterium accumulate intracellular volutin granules (metachromatic granules) which stain reddish purple with dilute methylene blue.
6. The cell walls of Corynebacterium contain mycolic acid containing ______________ carbon atoms.
a) 2 to 3
b) 100 to 150
c) 32 to 36
d) 20 to 25
Answer: c [Reason:] The cell walls of Corynebacterium contain mycolic acids (corynemycolic acids) containing 32 to 36 carbon atoms.
7. Cells of Arthrobacter in the stationary phase of growth are ____________ shaped.
d) rudimentary branching
Answer: c [Reason:] Cells of Arthrobacter in the stationary phase of growth are distinctly coccoid; when these are inoculated into fresh media, they give rise to rod-shaped cells.
8. Which of the following genus of species occur on the surface of certain cheeses such as brick and Limburger?
Answer: a [Reason:] B.linens of the Brevibacterium has its usual habitat on the surface of certain cheeses such as brick and Limburger, where it produces proteolytic enzymes that aid in the cheese-ripening process.
9. Which of the following genus of organisms are normal inhabitants of human mouth?
Answer: d [Reason:] The genus Rothia is aerobic,catalase-positive, and a normal inhabitant of the human mouth.
10. Mycobacteria are acid-fast organisms.
Answer: a [Reason:] A major characteristic of mycobacteria is that they are acid-fast; that is, once stained with aniline dyes, they are difficult to decolourize, even when treated with a mixture of acid and alcohol.
11. The causative agent of leprosy is ________________
Answer: b [Reason:] Mycobacterium leprae is the causative agent of leprosy.They may be slightly curved or straight rods.
12. The walls of Nocardioforms contains the sugars __________________________
a) sucrose and galactose
b) fructose and galactose
c) sucrose and arabinose
d) arabinose and galactose
Answer: d [Reason:] The walls of Nocardioforms contain the sugars arabinose and galactose.The peptidoglycan contains meso-diaminopimelic acid and no glycine interpeptide bridges occur between the peptidoglycan chains.
Interview MCQ Set 5
1. Who among the following was successful in raising 17 germ-free chickens for 40 days?
Answer: c [Reason:] In 1912, Cohendy at the Pasteur Institute raised 17 germ-free chickens for 40 days and concluded that vertebrate life is possible in the absence of microorganisms.
2. Within how many days after birth a stable flora develops?
a) 1 day
b) 7 days
c) 30 days
d) 7-14 days
Answer: d [Reason:] The initial flora may change considerably in composition during the first few days or weeks after birth until a stable flora becomes established and forms the normal flora.
3. Animals that are contaminated with germs are said to be gnotobiotic.
Answer: b [Reason:] Animals that are either germ-free or that live in association with one or more known organisms are said to be gnotobiotic.
4. How many day old embryonated eggs was used by Reyniers to rear first germ-free animals?
Answer: a [Reason:] The first germ-free animals reared by Reyniers were chickens obtained by sterilizing the shells of 20-day-old embryonated eggs.
5. Which among the following was the first germ-free animal to be reared?
a) guinea pigs
Answer: c [Reason:] The first germ-free animals reared by Reyniers were chickens obtained by sterilizing the shells of 20-day-old embryonated eggs with an effective germicide and placing them in sterile containers.
6. Which of the following vitamins are not required by normal animals?
a) Vit K
b) Vit B
c) Vit C
d) Vit A
Answer: a [Reason:] The germ-free animals require higher levels of Vitamin K, which normal animal do not require.
7. Germ-free animals require lower levels of B vitamins.
Answer: b [Reason:] Germ-free animals require higher levels of B vitamins than do normal animals, and they require vitamin K, which normal animals do not require.
8. Pseudomembranous colitis is caused by the strains of which of the following microorganism?
a) Streptococcus mutans
b) Clostridium difficile
c) Streptococcus salivarius
d) Clostridium botulinum
Answer: b [Reason:] Pseudomembranous colitis is a severe disease caused by excessive growth of toxin-producing strains of Clostridium difficile.
9. Where does the Streptococcus mutans adhere to the body site?
a) intestinal tract
Answer: c [Reason:] Microorganisms may often adhere specifically to one body site. Streptococcus mutans selectively binds to the smooth surface of the teeth.
10. Which of the following microorganism produces colicins in intestine?
c) Clostridium botulinum
d) Streptococcus salivarius
Answer: a [Reason:] Many strains of E.coli in the intestines produce colicins which may help to protect the intestinal tract from closely related pathogenic bacteria.