Category: MICROBIOLOGY Objective Questions

Microbiology Multiple Choice Questions on “Animals and Plants – Viruses and Vaccination”.

1. From which of the following animal was the material isolated which was used for the vaccination for the first time?
A. cat
B. cow
C. pig
D. goat
Answer: B
Clarification: Jenner used the material isolated from cows to be used as vaccination and it provided protection against natural smallpox infection.

2. Vaccination was invented by ____________
A. Jenner
B. Pasteur
C. Watson
D. Crick
Answer: A
Clarification: In 1796 Jenner first vaccinated an 8-year old boy with material removed from cow and it gave protection against the smallpox virus.

3. Causative agent of tobacco mosaic disease was filterable.
A. True
B. False
Answer: A
Clarification: In 1892, Dmitrii Ivanowski discovered that the causative agent of tobacco mosaic disease was filterable. Viruses that can pass through porcelain filters are known as filterable viruses.

4. Yellow fever virus can be attenuated by serial passage on cultures of ______________
A. embryonated eggs
B. tissue
C. chick embryo tissue
D. pig embryo tissue
Answer: C
Clarification: Max Theiler found in 1937 that virulent yellow fever virus can be attenuated by serial passage on cultures of chick embryo tissue.

5. Effective poliomyelitis vaccines were developed by culturing the virus of poliomyelitis on the kidney cells of which animal?
A. cow
B. monkey
C. giraffe
D. pig
Answer: B
Clarification: Enders, Robbins, and Weller laid the foundation for the development of effective poliomyelitis vaccines by culturing the virus of poliomyelitis on monkey kidney cells in 1949.

6. For which viral disease, vaccine has been recently developed through the use of tissue culture?
A. Measles
B. Mumps
C. Rabies
D. S mallpox
Answer: A
Clarification: Among the virus diseases for which vaccines have been recently developed through the use of tissue culture is measles (rubeola).

7. Rubella vaccines contain viruses are isolated only in African green monkey cells.
A. True
B. False
Answer: B
Clarification: Rubella vaccines contain viruses either isolated in African green monkey cells and attenuated by further cell passage (in primary duck embryo cells) or isolated and passed to diploid human embryo cells.

8. Translation of mRNA into proteins takes place in the ________________
A. host cell nucleus
B. host cell cytoplasm
C. viral nucleus
D. viral cytoplasm
Answer: B
Clarification: Translation of mRNA into proteins takes place in the host cell cytoplasm and uses ribosomes, transfer RNAs, and enzymes in the cytoplasm.

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Microbiology Multiple Choice Questions on “Distribution and Techniques for the Study of Aquatic Microorganisms”.

1. Protozoa and other minute animal life are known as ____________________
A. plankton
B. phytoplankton
C. zooplankton
D. mycoplankton
Answer: C
Clarification: The aggregation of floating and drifting microbial life in the surface region of the aquatic ecosystem is called plankton. Protozoa and other minute animal life are known as zooplankton.

2. Microbial inhabitants of the bottom region of a body of water are referred to as ________________
A. phytoplankton
B. benthic organisms
C. zooplankton
D. mycoplankton
Answer: B
Clarification: Microbial inhabitants of the bottom region of a body of water are referred to as the benthic organisms. The richest region of an aquatic system in terms of numbers and kinds of organisms is the benthic region.

3. Phytoplanktonic organisms are non-motile.
A. True
B. False
Answer: B
Clarification: Most phytoplanktonic organisms are motile, possess some structural features or contain oil droplets which give them buoyancy.

4. Which of the following places shows the presence of Geothermal vents?
A. Coasts of California
B. Coasts of Peru
C. Galapagos islands
D. Pacific ocean
Answer: C
Clarification: It has been calculated that geothermal vents such as the one near the Galapagos Islands account for most of the nutrients dissolved in the oceans of the world.

5. Large spiraling surface currents in the ocean that tend to aggregate and retain nutrients are known as _______________
A. benthic region
B. upwelling
C. geothermal vents
D. gyres
Answer: D
Clarification: Gyres are large spiraling surface currents in the ocean that tend to aggregate and retain nutrients, wastes, and microorganisms. Gyres have only been appreciated in recent years, through the use of satellite imagery.

6. Most aquatic microorganisms can grow on the usual laboratory media.
A. True
B. False
Answer: B
Clarification: Many aquatic microorganisms will not grow on the usual laboratory media such as nutrient agar or nutrient broth and consequently, cannot be isolated.

7. Which of the following techniques is used for identification and enumeration of algae, bacteria, protozoa?
A. Microscopic examination
B. Submerged-slide technique
C. Membrane-filter technique
D. Enrichment-culture technique
Answer: A
Clarification: Microscopic examination for identification and enumeration of algae, bacteria, protozoa, and many fungi is carried out.

8. Which of the following techniques can be used to separate different-size fractions of the aquatic microbial community?
A. submerged-slide technique
B. fluorescent antibody technique
C. membrane-filter technique
D. by measuring biochemical activity
Answer: C
Clarification: Membrane-filter technique is applicable for the examination and cultivation of many bacteria from the aquatic environments. It can also be used to separate different-size fractions of the aquatic microbial community.

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Microbiology Multiple Choice Questions on “Bacterial Transformation”.

1. What are the characteristics of rough pneumococci strain?
A. noncapsulated and pathogenic
B. noncapsulated and nonpathogenic
C. capsulated and pathogenic
D. capsulated and nonpathogenic
Answer: B
Clarification: Griffith injected mice with a few rough (noncapsulated and nonpathogeniC. pneumococci and a large number of heat-killed smooth cells.

2. In Griffith’s experiment which of the following strains of pneumococci was isolated from dead mice?
A. live rough cells
B. dead rough cells
C. live smooth cells
D. dead smooth cells
Answer: C
Clarification: When Griffith injected mice with a mixture of a few rough and a large number of heat-killed smooth cells of pneumococci, then the mice subsequently died of pneumonia, and live smooth cells were isolated from their blood.

3. Which of the following things was identified as the transforming principle?
A. DNA
B. RNA
C. Proteins
D. Carbohydrates
Answer: A
Clarification: Griffith showed in his experiment that DNA was the transforming principle that transformed the living rough bacteria into pathogenic smooth ones.

4. We require cell-free DNA for transformation to take place.
A. True
B. False
Answer: A
Clarification: Transformation is the process whereby cell-free or naked DNA containing a limited amount of genetic information is transferred from one bacterial cell to another.

5. What should be the minimum weight of DNA that is required for a successful transformation?
A. 1000 daltons
B. 100,000 daltons
C. 300,000 daltons
D. 8 million daltons
Answer: C
Clarification: Molecular weights of DNA in the range of 300,000 to 8 million daltons have been shown to result in successful transformation.

6. How many DNA molecules are transferred after each transformation?
A. 2
B. 1
C. 50
D. infinite
Answer: B
Clarification: Each transformation results from the transfer of a single DNA molecule of double-stranded DNA.

7. Which of the following enzymes acts on the DNA after its entry into the cell?
A. ligases
B. endonucleases
C. deoxyribonucleases
D. exonucleases
Answer: C
Clarification: After DNA entry into a cell, one strand is immediately degraded by deoxyribonucleases, while the other strand undergoes base pairing with a homologous portion of the recipient cell chromosome.

8. Which among the following species have not been transformed?
A. Bacillus
B. Neisseria
C. Rhizobium
D. Aspergillus
Answer: D
Clarification: Bacterial species that have been transformed include, besides Streptococcus pneumonia, those in the genera Bacillus, Haemophilus, Neisseria, and Rhizobium.

9. In which phase of growth does the recipient cell take up the donor DNA?
A. lag phase
B. early logarithmic phage
C. late logarithmic phage
D. stationary phage
Answer: C
Clarification: Conditions suitable for uptake of donor DNA into recipient cells occur only during the late logarithmic phase of growth.

10. The DNA uptake process does not require any energy.
A. True
B. False
Answer: B
Clarification: The uptake process has been found to be an energy-requiring mechanism because it can be inhibited by agents that interfere with energy metabolism.

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Microbiology Multiple Choice Questions on “Microorganisms Microscopic Examination – Microbial Stains”.

1. The dye eosinate of methylene blue belongs to which group?
A. Acidic dye
B. Basic dye
C. Neutral dye
D. Oxazine dye
Answer: C
Clarification: A neutral dye is a complex salt of a dye acid with a dye base so eosinate of methylene blue is an example of a neutral dye. An acidic dye is one in which the charge on the dye ion is negative and a basic dye is one in which the charge carried by the dye ion is positive.

2. What is the correct order of staining reagents in Gram-Staining?
A. Crystal violet, alcohol, iodine solution, safranin
B. Crystal violet, iodine solution, alcohol, safranin
C. Crystal violet, safranin, alcohol, iodine solution
D. Iodine solution, crystal violet, alcohol, safranin
Answer: B
Clarification: Gram staining is a type of differential staining. In this process the fixed bacterial smear is subjected to the following staining reagents in the order listed: crystal violet, iodine solution, alcohol (decolorizing agent), and safranin.

3. Which bacteria appears purple-violet colour after staining?
A. Gram-positive
B. Gram-negative
C. Both Gram-positive and Gram-negative
D. Neither Gram-positive nor Gram-negative
Answer: A
Clarification: Gram-positive bacteria retain the crystal violet and hence appear deep purple-violet colour as it has a higher content of the peptidoglycan layer. Gram-negative bacteria have lesser amount of peptidoglycan layer and on treatment with alcohol it loses the purple-violet colour, are counterstained by safranin and hence appears red.

4. Which of the following are true for Gram-negative bacteria?
A. upon alcohol treatment, the permeability of the cell wall increases
B. crystal violet-iodine (CV-I) complex is extracted
C. pore size decreases and the CV-I complex cannot be extracted
D. alcohol treatment increases the permeability of the cell wall and the CV-I complex can be extracted
Answer: D
Clarification: Experimental evidence suggests that during staining of Gram-negative bacteria the alcohol treatment extracts the lipid, which results in increased permeability of the cell wall. Thus the crystal violet-iodine (CV-I) complex can be extracted and the Gram-negative organism is decolorized. These cells subsequently take on the color of the safranin counterstain.

5. Gram-positive bacteria are usually more susceptible to?
A. streptomycin
B. tetracyclin
C. penicillin
D. ampicillin
Answer: C
Clarification: Gram-positive bacteria are usually more susceptible to penicillin and less susceptible to disintegration by mechanical treatment or exposure to some enzymes than Gram-negative bacteria. Gram-negative bacteria are more susceptible to other antibiotics like streptomycin.

6. Which of the staining technique helps in demonstrating spore structure in bacteria as well as free spores?
A. Acid-fast stain
B. Endospore stain
C. Capsule stain
D. Flagella stain
Answer: B
Clarification: There are numerous other staining techniques designed to identify some particular feature of cell structure or composition. Endospore staining demonstrates spore structure in bacteria as well as free spores.

7. In Gram-staining, iodine is used as a ______________
A. fixative
B. mordant
C. solublizer
D. stain
Answer: B
Clarification: In Gram-staining, iodine acts as a mordant i.e. it combines with the dye or stain and thereby fixes it on the material. It increases the interaction between the stain solution and the bacterial cell.

8. Which of the following is the example of Gram-negative bacteria?
A. Lactobacillus
B. Eschericia coli
C. Staphylococcus aureus
D. Bacillus subtilis
Answer: B
Clarification: Eschericia coli is an example of Gram-negative bacteria. Others are all examples of Gram-positive bacteria.

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Microbiology Multiple Choice Questions on “Energy Production by Aerobic Processes”.

1. The TCA Cycle is an _____________ pathway.
A. catabolic
B. anabolic
C. amphibolic
D. respiratory
Answer: C
Clarification: The TCA cycle is an amphibolic cycle which means that it functions not only in catabolic (breakdown) but also in anabolic (synthesis) reactions.

2. Which of the following intermediates of TCA cycle act as amino acid precursors?
A. oxaloacetic acid
B. succinic acid
C. citric acid
D. acetyl CoA
Answer: A
Clarification: Oxaloacetic acid and alpha-ketoglutaric acid are some of the intermediates of TCA cycle which act as amino acid precursors.Oxaloacetate forms aspartate which then gives us lysine and threonine.

3. Which pathway will result in the production of four carbon dioxide molecules, two ATP molecules, NADH₂ and FADH₂?
A. glycolysis
B. Krebs cycle
C. Calvin cycle
D. electron transport system
Answer: B
Clarification: Krebs Cycle is another name for TCA cycle whose overall reaction is as follows:
2Acetyl CoA+ 3H₂O + 3NAD+ + FAD+ ADP+ Pi———> 4CO₂+ 2CoA+ 2NADH₂+ 2FADH₂+ ATP.

4. The TCA cycle is regulated by which of the following enzymes?
A. citrate synthase
B. isocitrate dehydrogenase
C. malate dehydrogenase
D. succinate dehydrogenase
Answer: B
Clarification: TCA cycle is regulated by the enzyme isocitrate dehydrogenase which is sensitive to feedback inhibition by high concentration of ATP and NADH₂ and stimulation by high concentration of ADP and NAD.

5. Protein molecules can easily pass into the cell for being utilized for energy production.
A. True
B. False
Answer: B
Clarification: Protein molecules are too large to pass into the cell, bacteria secrete exoenzymes called proteases that hydrolyze exogenous proteins to peptides, which are then transported into the cell cytoplasm.

6. Which of the following pathway is common for oxidation of carbohydrates, lipids and amino acids?
A. Calvin cycle
B. Electron transport chain
C. TCA cycle
D. Pentose phosphate pathway
Answer: C
Clarification: Since acetyl-CoA is a common intermediate of carbohydrate, lipid, and amino acid metabolism so it enters the TCA cycle and hence TCA cycle is a common pathway for oxidation of carbohydrates, lipids and amino acids.

7. Phosphoenolpyruvate (PEP) is converted to oxaloacetate by the enzyme PEP deaminase.
A. True
B. False
Answer: B
Clarification: PEP is converted to oxaloacetate by the enzyme PEP carboxylase. This is a type of carbon dioxide fixing reaction.

8. The enzymes present in glyoxylate cycle are which type of enzymes?
A. reductase enzymes
B. anaplerotic enzymes
C. transferase enzymes
D. hydrolase enzymes
Answer: B
Clarification: The specific enzymes for glyoxalate cycle are isocitrate lyase and malate synthase which carry out replenishment of the pool of intermediates of the TCA cycle and hence are known as anaplerotic enzymes.

9. Which molecule will combine with the four-carbon oxaloacetate in the TCA cycle to form the six-carbon citrate?
A. lactic acid
B. NADH
C. ATP
D. acetyl-CoA
Answer: D
Clarification: The first step of the TCA cycle is the reaction between oxaloacetate and acetyl-CoA to form citrate. This acetyl-CoA comes from carbohydrate, lipid metabolism.

10. The number of ATP molecules generated in TCA cycle is _________
A. 34
B. 38
C. 24
D. 12
Answer: C
Clarification: In TCA cycle the following result is obtained:
6 NADH₂ —> 18 ATP
2 FADH₂ —> 4 ATP
2 GTP —> 2 ATP
Thus, total ATP = 24 ATP.

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Microbiology Multiple Choice Questions on “Fungi – Molds and Yeasts – Morphology”.

1. Fungi are ______________
A. prokaryotic
B. eukaryotic
C. prokaryotic and lack chlorophyll
D. eukaryotic and lack chlorophyll
Answer: D
Explanation:Fungi are eucaryotic spore-bearing protists that lack chlorophyll. They are of great practical and scientific interest to microbiologists.

2. Hyphal wall consists of microfibrils composed of ___________________
A. hemicellulose or chitin
B. cellulose
C. lipids
D. proteins
Answer:a
Clarification: The hyphal walls of fungi consist of microfibrils composed for the most part of hemicellulose or chitin; true cellulose occurs only in the walls of lower fungi.

3. Coenocytic hyphae have ________________
A. septate with uninucleate cells
B. septate with multinucleate cells
C. no septate
D. no septate with uninucleate cells
Answer: C
Clarification: Coenocytic hyphae are also known as nonseptate hyphae and hence have no sep-ta.

4. What are the dimensions of the filaments that the thallus of a fungus consists of?
A. 1 micrometre
B. 5 to 10 micrometre
C. 1 metre
D. 1 centimetre
Answer: B
Clarification: The thallus or body of a fungus consists of filaments, 5 to 10 micrometre across, which are commonly branched.

5. The yeast cell or mould filament is surrounded by a true cell wall.
A. True
B. False
Answer: A
Clarification: The yeast cell or mould filament is surrounded by a true cell wall. The exception being the slime moulds, which have a thallus consisting of a naked amoeboid mass of proto-plasm.

6. What do the term dimorphic mean?
A. Bisexual
B. Unisexual
C. Exists in two forms
D. Exists in single form
Answer: C
Clarification: Some fungi are dimorphic, that is, they exist in two forms. Some pathogenic fungi have a unicellular and yeastlike form in their host, but when growing saprophytically in soil or in laboratory medium they have a filamentous mold form.

7. Yeasts have flagella for the purpose of locomotion.
A. True
B. False
Answer: B
Clarification: Yeasts have no flagella or other organelles of locomotion.

8. The crosswalls constrict which of the following parts and then grow inwards to form septum?
A. hyphae
B. lumen
C. protoplasm
D. plasmalemma
Answer: D
Clarification: The crosswalls constrict the plasmalemma and grow inward to form generally an incomplete septum that has a central pore which allows for protoplasmic streaming.

9. Which of the following surrounds plasmalemma?
A. lumen
B. wall
C. protoplasm
D. hyphae
Answer: C
Clarification: Between the protoplasm and the wall is the plasmalemma, a double-layered mem-brane which surrounds the protoplasm.

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