Category: MICROBIOLOGY Objective Questions

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

1. How many dsRNA segments are present in the reovirus genome?
A. 1
B. 3
C. 50
D. 10
Answer: D
Clarification: Reoviruses contain both the + and the — strands of dsRNA and its genome consists of 10 dsRNA segments. During uncoating ten mRNA molecules are transcribed from one strand of the dsRNA and pass into the host cell cytoplasm.

2. Enterovirus belongs to which of the following family of viruses?
A. Tymovirus
B. Picornaviridae
C. Reoviridae
D. Closterovirus
Answer: B
Clarification: Enterovirus belongs to the family Picornaviridae and it has a virion size of 28 nm.

3. Rous sarcoma virus consists of RNA as its genetic material.
A. True
B. False
Answer: A
Clarification: Rous sarcoma virus belongs to Retroviridae family, has a virion size of 100-120. It possesses icosahedral symmetry and consists of RNA as its genetic material.

4. Which of the following viruses possess an envelope?
A. Herpesvirus
B. Reovirus
C. Tobacco mosaic virus
D. Papillomavirus
Answer: A
Clarification: Herpesvirus possesses an icosahedral symmetry and contains DNA as its genetic material. Its nucleocapsid is surrounded by an envelope.

5. Which of the following viruses have a complex symmetry?
A. Alphavirus
B. Mobillivirus
C. Orthopoxvirus
D. Parvovirus
Answer: C
Clarification: Orthopoxvirus posseses a complex symmetry and is surrounded by a coat. It consists of DNA as its nucleic acid.

6. The family of Rhabdoviridae possesses dsRNA.
A. True
B. False
Answer: B
Clarification: The family of Rhabdoviridae consists of ssRNA and they are enveloped. An example is vesicular stomatitis.

7. Cowpea virus belongs to which of the following group of viruses?
A. Comovirus
B. Dianthovirus
C. Cucumovirus
D. Carlavirus
Answer: A
Clarification: Cowpea mosaic belongs to the Comovirus group of viruses. They are non-enveloped and possess ssRNA.

8. For the cultivation of viruses the fertile chicken eggs should be incubated for how many day(s)?
A. 1
B. 2-4
C. 5-12
D. 2-7
Answer: C
Clarification: For the cultivation of viruses by embryonated chicken eggs, the fertile chicken eggs should be incubated for 5 to 12 days and then they can be inoculated through the shell aseptically.

9. Which of the following method is used for the production of vaccines against yellow fever?
A. tissue-culture method
B. chick-embryo method
C. through susceptible animals
D. through appropriate media
Answer: B
Clarification: The chick-embryo technique has been used in the production of vaccines against smallpox, yellow fever, influenza, and other diseases and in immunologic tests and other studies whenever large amounts of virus are required.

10. The karyotype of cells formed from continuous cell lines is _______________
A. haploid
B. diploid
C. aneuploid
D. haploid and diploid
Answer: C
Clarification: The karyotype of cells cultured through continuous cell lines is aneuploid i.e., a variable multiple of the haploid chromosome number and not diploid.

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Microbiology Multiple Choice Questions on “Productivity of Aquatic Microorganisms”.

1. The primary producers in the marine system are ________________
A. protozoa
B. cyanobacteria
C. fungi
D. cyanobacteria and eukaryotic algae
Answer: D
Clarification: The primary producers in the marine system are cyanobacteria and eukaryotic algae which predominate in the phytoplankton.

2. The primary producers transform radiant energy into heat energy.
A. True
B. False
Answer: B
Clarification: The primary producers through photosynthesis, are capable of transforming radiant energy into chemical energy (organic compounds).

3. The biological activity of an aquatic ecosystem is dependent upon which of the following factors?
A. number of primary producers
B. amount of chemical energy produced
C. rate of primary production
D. number of deaths of organisms
Answer: C
Clarification: The biological activity of an aquatic ecosystem is dependent upon the rate of primary production performed by the photosynthetic organisms.

4. n which of the following water bodies, the role of photosynthetic organisms is considerably reduced?
A. Lakes
B. Ponds
C. Estuaries
D. Streams
Answer: C
Clarification: In shallow estuaries the role of photosynthetic organisms as primary producers is considerably reduced. Plant growth from the shoreline contributes leaves, stems, and roots of vegetation and other organic detritus.

5. Which of the following aquatic organisms contribute in a small amount to the shallow estuary food web?
A. benthic algae
B. bacteria
C. protozoa
D. nematodes
Answer: A
Clarification: Phytoplankton and benthic algae make a small contribution to the food supply in the food web of shallow estuaries.

6. Which among the following are referred to as the “pasture of the sea”?
A. fishes
B. algae
C. nematodes
D. phytoplankton
Answer: D
Clarification: Plankton, particularly phytoplankton, has been referred to as the “pasture of the sea”. Fish, whales, and squids feed directly on plankton or on larger plankton-feeding animals.

7. The term fertility of oceans is used to express the capacity for the production of inorganic matter.
A. True
B. False
Answer: B
Clarification: The term fertility of oceans is used to express the capacity for the production of organic matter by the organisms present in these waters.

8. What amount of dry organic matter is produced by deep ocean areas?
A. 1g
B. 10g
C. 0.5g
D. 100g
Answer: C
Clarification: The terrestrial environment produces 1 to 10 g of dry organic matter per square meter per day compared to 0.5 g for the deep ocean areas.

9. Which among the following factors are limiting the growth of phytoplankton organisms?
A. carbon dioxide
B. radiant energy
C. water
D. radiant energy,nitrogen
Answer: D
Clarification: The factors generally limiting growth are radiant energy, nitrogen and phosphorus, and the trace elements. The nitrogen, phosphorus and trace elements are made available through the mineralization reactions of microorganisms.

10. Which among the following oceans is the most richest in life?
A. Antarctic Ocean
B. Atlantic Ocean
C. Pacific Ocean
D. Indian Ocean
Answer: A
Clarification: The Antarctic Ocean is described as being richer in life than any other major oceanic area. The richness of nutrients in this region is attributable to the mixing of the waters of the Atlantic, Pacific, and Indian Oceans.

11. In which of the following water bodies, fertility is high?
A. open sea
B. coastal regions
C. lakes
D. rivers
Answer: B
Clarification: Although coastal and estuarine regions provide a less stable physical environment, their fertility exceeds that of the open sea because of the large amounts of nutrients available.

12. Which of the following product is not obtained from dissimilation of organic matter under aerobic conditions?
A. ammonium
B. sulphate
C. methane
D. phosphate
Answer: C
Clarification: Under aerobic conditions the principal products resulting from dissimilation of organic compounds are ammonium, carbon dioxide, sulphate, and phosphate.

13. Which of the following organism have siliceous skeletons?
A. Foraminifera
B. Coccolithophores
C. Radiolaria
D. Cyanobacteria
Answer: C
Clarification: Radiolaria and silicoflagellates have siliceous skeletons whereas foraminifera and coccolithophores produce calcareous skeletons.

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Microbiology online quiz focuses on “Microbial Flora of Healthy Human Host – Distribution and Occurrence of the Normal Flora”.

1. Which of the following viruses are termed as ‘orphan’ viruses?
A. retroviruses
B. echoviruses
C. coxsackieviruses
D. adenoviruses
Answer: B
Clarification: Certain human intestinal viruses were discovered only by noting their cytopathogenic effects in tissue cultures; thus they were termed as ‘orphan’ viruses or echoviruses.

2. Bacteria can be grown on the dry surface of skin.
A. True
B. False
Answer: B
Clarification: The relatively dry surface of the skin is inhibitory to microbial growth. Moist regions of the skin have higher numbers of normal flora.

3. Which of the following causes the disease acne vulgaris?
A. Staphylococcus epidermis
B. Diphtheroids
C. P.acnes
D. E.coli
Answer: C
Clarification: In the deep sebaceous glands are found lipophilic anaerobic bacteria such as Propionibacterium acnes which is associated with the skin disease known as acne vulgaris.

4. Which of the following bacteria are found in the nose?
A. Haemophilus sp.
B. S. pneumoniae
C. Corynebacterium sp.
D. S. epidermidis
Answer: D
Clarification: The bacteria most frequently and most consistently found in the nose are S. epidermidis and S. aureus.

5. The microorganisms stick to which of the following regions of the respiratory tract?
A. nasal baffle
B. nasopharynx
C. mucus
D. oropharynx
Answer: C
Clarification: Microorganisms will impinge on and stick to the thin moist layer of highly viscous mucus that overlies the surface of the respiratory tract.

6. Alveolar macrophages are phagocytic in nature.
A. True
B. False
Answer: A
Clarification: Bacteria that manage to travel the air passages all the way to the alveoli of the lungs are usually engulfed and destroyed by phagocytic body cells known as alveolar macrophages.

7. Saliva generally has a microbial population of _______ bacteria per milliliter.
A. 100
B. 1000
C. 105
D. 108
Answer: D
Clarification: Saliva itself generally contains transient microbes from other sites of the oral cavity, particularly from the upper surface of the tongue, and generally has a microbial population of about 108 bacteria per milliliter.

8. Fusobacterium belongs to which type of bacterial group?
A. aerobes
B. facultative anaerobes
C. obligate anaerobes
D. microaerophilic
Answer: C
Clarification: As the first teeth appear, obligate anaerobes, such as species of the genera Bacteroides and Fusobacterium, become more evident because the tissue surrounding the teeth provides an anaerobic environment.

9. Which enzyme is required for the production of glucan?
A. glycosyl transferase
B. glucoisomerase
C. hexokinase
D. glucose-6-phosphatase
Answer: A
Clarification: Glucan is formed only in the presence of the disaccharide sucrose by means of an enzyme called glycosyl transferase located on the surface of the cocci.

10. Which of the following microorganism is found in the gingival crevices at puberty?
A. Lactobacillus
B. Treponema sp.
C. Actinomyces
D. S.mutans
Answer: B
Clarification: Probably as a result of hormonal changes, anaerobic bacteria, especially oral spirochetes like Treponema sp. and Bacteroides melaninogenicus, colonize the oxygen-deficient gingival crevices at puberty.

11. Enterococci is found in which part of the intestine?
A. duodenum
B. jejunum
C. ileum
D. large intestine
Answer: B
Clarification: In the jejunum there are occasionally found species of enterococci, lactobacilli, and diphtheroids.

12. Which body part contains the largest microbial population?
A. stomach
B. small intestine
C. large intestine
D. mouth
Answer: C
Clarification: In the human body the colon or large intestine has the largest microbial population. It has been estimated that the number of microorganisms in stool specimens is about 1011 organisms per gram wet weight.

13. Which of the following is not a Gram-positive bacilli?
A. Bacteroides
B. Eubacterium
C. Lactobacillus
D. Bifidobacterium
Answer: A
Clarification: The Gram-positive bacilli are represented mainly by species of Bifidobacterium, Eubacterium, and Lactobacillus. But Bacteroides are anaerobic Gram-negative bacilli.

14. Which microorganism among the following can live as a commensal but can also be pathogenic?
A. Trichomonas hominis
B. Entamoeba histolytica
C. Endolimax
D. Iodamoeba
Answer: B
Clarification: Entamoeba histolytica can live as a commensal but can also be pathogenic, causing amoebic dysentery; it is capable of penetrating the intestinal mucosa and invading various organs of the body.

To practice all areas of Microbiology for online Quizzes, .

Microbiology Multiple Choice Questions on “Morphology and Fine Bacteria – Structures External to the Cell Wall”.

1. Bacteria having clusters of flagella at both poles of cells are known as?
A. Lophotrichous
B. Peritrichous
C. Amphitrichous
D. Monotrichous
Answer: C
Clarification: In amphitrichous, flagella occur either singly or in clusters at both cell poles. Lophotrichous refers to a cluster of polar flagella, peritrichous is surrounded by lateral flagella and monotrichous is for a single polar flagella.

2. Salmonella typhi has which type of flagella arrangement?
A. Amphitrichous
B. Peritrichous
C. Monotrichous
D. Lophotrichous
Answer: B
Clarification: Salmonella typhi has peritrichous type of flagella arrangement. In peritrichous, the bacteria are surrounded by lateral flagella.

3. The L Ring in Gram-Negative bacterium flagella is associated with _________
A. Peptidogycan
B. Outer Membrane
C. Cytoplasmic Membrane
D. Cell Membrane
Answer: B
Clarification: The flagella in Gram-Negative bacteria has four basal rings. The L Ring of flagella is associated with the outer membrane. The P ring is associated with the peptidoglycan layer and both the M and S rings are associated with the cytoplasmic membrane.

4. Which among the following acts as a transport protein for protons in flagellar motion?
A. fli protein
B. cGMP
C. atp
D. mot protein
Answer: D
Clarification: The proton binds to the Mot protein and this changes the conformation of Mot protein. It results in releasing the ring and helps in flagellar motion. The fli protein helps in changing the direction of flagella.

5. F pilus has a major role as ___________
A. motility of the cell
B. port of entry of genetic material during mating
C. attachment to host cell
D. human infection
Answer: B
Clarification: Pili are hollow, filamentous appendages that are thinner and shorter. They do not function in motility and have other different functions. One type known as F plus or sex plus serves as the port of entry of genetic material during bacterial mating.

6. Prosthecae helps in __________
A. motility
B. nutrient absorption and attachment to surfaces
C. human infection
D. protection from the environment
Answer: B
Clarification: Prosthecae increases the surface area of the cells for nutrient absorption, which is advantageous in dilute environments. Some prosthecate bacteria have an adhesive substance at the end of a prostheca that aids in attachment to surfaces.

7. The capsule of Klebsiella pneumoniae is composed of heteropolysaccharides.
A. True
B. False
Answer: A
Clarification: Heteroploysaccharides are usually synthesized from sugar precursors that are activated within the cell, attached to a lipid carrier molecule, transported across the cytoplasmic membrane and polymerized outside the cell. The capsule of Klebsiella pneumoniae is an example of heteropolysaccharides.

8. When a bacteria swim towards a chemical, it is termed as__________
A. positive chemotaxis
B. phototaxis
C. negative chemotaxis
D. magnetotaxis
Answer: A
Clarification: When a bacteria swim towards or away from chemical compounds, the phenomenon is known as bacterial chemotaxis. Swimming towards a chemical is termed as positive chemotaxis; swimming away is negative chemotaxis.

9. Which type of force drives the flagellar motion?
A. Protonmotive force
B. ATP driven
C. Protonmotive and ATP driven
D. No protonmotive nor ATP driven
Answer: A
Clarification: It is found that the flagellar motor is driven by the protonmotive force, i.e., the force derived from the electrical potential and the hydrogen-ion gradient across the cytoplasmic membrane.

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Microbiology Questions and Answers for Experienced people focuses on “Utilization of Energy in Nonbiosynthetic Processes”.

1. Which of the following has no detectable ATPase activity?
A. cilia
B. eukaryotic flagella
C. bacterial flagella
D. endoflagella
Answer: C
Clarification: Bacterial flagella appears to have no machinery for interconverting chemical and mechanical energy. Flagellin, the flagellar protein molecule, has no enzymatic activity i.e. no detectable ATPase activity.

2. Which force drives the flagellar rotation in bacteria?
A. ATP
B. protonmotive force
C. electrons
D. water gradient
Answer: B
Clarification: The flagellar motor is driven by the protonmotive force, i.e., the force derived from the electric potential and the hydrogen gradient across the cytoplasmic membrane and not ATP.

3. Rotary motor of flagella is associated with _________
A. M ring
B. P ring
C. L ring
D. M and S ring
Answer: D
Clarification: The rotary motor is believed to be the two elements in the basal body, the M ring and the S ring. The rod (which is connected to the filament by the hook) is fixed rigidly to the M ring, which rotates freely in the cytoplasmic membrane. The S ring is mounted rigidly on the cell wall.

4. Passive diffusion requires the use of membrane transport proteins for the transport of solute molecules across the membrane.
A. True
B. False
Answer: B
Clarification: In passive diffusion no substance in the membrane interacts specifically with the solute molecules. The difference in concentration gradient governs the rate of the inward flow of solute molecules.

5. The entry of glycerol into the bacterial cells is by ____________
A. passive diffusion
B. facilitated diffusion
C. group translocation
D. active diffusion
Answer: B
Clarification: The entry of glycerol into the bacterial cells is an example of facilitated diffusion which involves the use of a specific protein carrier molecule called a porter for the diffusion of solutes.

6. Porter or permease is located in the _______________
A. cytoplasmic membrane
B. cell membrane
C. nuclear membrane
D. outer membrane
Answer: A
Clarification: Porter or permease is a specific protein carrier molecule that is required in facilitated diffusion which combines reversibly with the solute molecules and releases it into the inside of cell.

7. Facilitated diffusion does not require metabolic energy.
A. True
B. False
Answer: A
Clarification: Both the passive diffusion and facilitated diffusion does not require metabolic energy.

8. The reaction for the transfer of phosphoryl group of phosphoenol pyruvate to the sugar molecule requires which ion?
A. Mg²⁺
B. Fe²⁺
C. O
D. PO₄^2-
Answer: A
Clarification: The reaction for the transfer of phosphoryl group of phosphoenol pyruvate to the sugar molecule requires Mg²⁺, the products formed are sugar phosphate and pyruvate.

9. HPr stands for ______________
A. heat-stable carrier protein
B. hydrogen carrier protein
C. pyruvate dehydrogenase
D. high-energy protein
Answer: A
Clarification: Heat-stable protein (HPr) is activated first by transfer of phosphate group from the high-energy compound phosphoenol pyruvate inside the cell.

10. In phosphotransferase system(PTS), the sugar-phosphate is released inside the cell by which of the following?
A. Enzyme I
B. Enzyme II
C. Enzyme III
D. HPr
Answer: B
Clarification: Enzyme II is specific for a particular sugar, and is an integral component of the cytoplasmic membrane. Here it combines with the phosphate group carried by the activated HPr.The sugar-phosphate is released by enzyme II and enters the cell.

11. Mannitol enzyme II has been purified from _____________
A. E.coli
B. Salmonella typhimurium
C. Saccharomyces cerevisiae
D. Lactobacillus
Answer: A
Clarification: Mannitol enzyme II has been purified from E.coli. Other enzymes can be purified from several other bacteria.

To practice all areas of Microbiology for Experienced people, .

Microbiology Multiple Choice Questions on “Physiology and Cultivation of Fungi”.

1. Pathogenic fungi have a temperature optimum at __________
A. 30 to 37 degree celsius
B. 22 to 30 degree celsius
C. 37 to 42 degree celsius
D. 42 to 50 degree celsius
Answer: A
Clarification: Fungi grow over a wide range of temperatures. Pathogenic species have a higher temperature optimum, generally 30 to 37 degree Celsius.

2. Sabouraud media for the growth of fungi is composed of ____________________
A. glucose and ammonia
B. maltose and peptone
C. sucrose and peptone
D. peptone
Answer: B
Clarification: One of the best known and oldest media for the growth of fungi is Sabouraud media that contains maltose and peptone as its principal ingredients.

3. Sabouraud media has ________________
A. high ph, low sugar concentration
B. high ph, moderate sugar concentration
C. low ph, high sugar concentration
D. low ph, moderate sugar concentration
Answer: C
Clarification: Sabouraud media is widely used for the isolation of molds and certain yeasts. Its partial selective action is due to the high sugar concentration and low pH.

4. Jams and jellies are spoiled by both bacteria and fungi.
A. True
B. False
Answer: B
Clarification: Yeasts and molds can grow in a substrate or medium containing concentrations of sugars that inhibit most bacteria; this is why jams and jellies may be spoiled by molds but not by bacteria.

5. What are the cell wall structural components of fungi?
A. peptidoglycan
B. cellulose
C. chitin
D. chitin,cellulose, or hemicellulose
Answer: D
Clarification: The cell wall structural components of fungi are chitin, cellulose, or hemicellulose whereas the bacterial cell wall is composed of peptidoglycan.

6. The optimum pH for the growth of fungi is ____________
A. 7.8-9.0
B. 12-14
C. 3.8-5.6
D. 1.0-2.0
Answer: C
Clarification: The optimum pH for the growth of fungi is 3.8-5.6. Acidic media (pH 5.6) are tolerated by molds but are inhibitory to most bacteria.

7. Which of the following are the oxygen requirements of molds?
A. Strictly aerobic
B. Facultatively aerobic
C. Anaerobic
D. Microaerophilic
Answer: A
Clarification: Moulds are strictly aerobic whereas yeasts are facultative organisms.

8. Fungi are sensitive to which of the following antibiotics?
A. penicillins
B. tetracyclins
C. chloramphenicol
D. griseofulvin
Answer: D
Clarification: Fungi are resistant to penicillins, tetracyclins, chloramphenicol but are sensitive to griseofulvin.

9. Ordinary inoculating loop can be used for inoculation of yeasts.
A. True
B. False
Answer: A
Clarification: Ordinary inoculating loop used for bacteria is suitable for the inoculation of yeasts. But the needle used for molds is stiffer and has a flattened tip for cutting the mycelium.

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