Category: MICROBIOLOGY Objective Questions

250+ TOP MCQs on Diseases Caused by Fungi and Answers

Microbiology Multiple Choice Questions on “Diseases Caused by Fungi”.

1. Dermatophytic diseases attributed infections to ______________
A. humans
B. insects
C. monkeys
D. birds
Answer: B
Clarification: Dermatophytic diseases attributed infections to insects and thus the Romans called these infections tinea, meaning “small insect larva”.

2. Fungus diseases that occur on the nails, skin, hair are referred to as systemic mycoses.
A. True
B. False
Answer: B
Clarification: Fungus diseases that occur on the nails, skin, hair, and mucous membranes are referred to as superficial mycoses or dermatomycoses.

3. Ringworm of the scalp is known as ______________
A. tinea capitis
B. tinea pides
C. tinea unguium
D. onychomycosis
Answer: A
Clarification: The dermatologists frequently used a terminology based on the part of the body involved, for example, tinea capitis is ringworm of the scalp.

4. Black piedra is a fungus infection of the ___________
A. skin
B. foot
C. hair
D. nails
Answer: C
Clarification: Black piedra is a fungus infection of hair, characterized by dark brown or black nodules on the hair shaft.

5. Which of the following causes epidemic ringworm of the scalp in children?
A. Microsporum audouinii
B. Trichophyton rubrum
C. Candida albicans
D. Epidermophyton floccosum
Answer: A
Clarification: Microsporum audouinii is a dermatophyte that causes epidemic ringworm of the scalp in children.

6. Tinea versicolor is caused by _______________
A. Piedraia hortae
B. Trichosporon beigelii
C. Malassezia furfur
D. Candida albicans
Answer: C
Clarification: Malassezia furfur causes tinea versicolor, a generalized fungus infection of the skin covering trunk and sometimes other areas of the body.

7. The systemic mycoses are caused mainly by air-borne organisms.
A. True
B. False
Answer: A
Clarification: The systemic mycoses are caused by many air-borne organisms that enter the body through the respiratory tract. They may however enter by other portals.

8. Moniliasis disease is caused by ________________
A. Histoplasma capsulatum
B. Blastomyces dermatitidis
C. Coccidioides immitis
D. Candida albicans
Answer: D
Clarification: Candida albicans causes Moniliasis that may infect any body tissue. It is found on mucous membranes of intestinal tracts.

9. Blastomyces brasiliensis causes which of the following disease?
A. North American blastomycosis
B. South American blastomycosis
C. Histoplasmosis
D. Sporotrichosis
Answer: B
Clarification: Blastomyces brasiliensis causes South American blastomycosis which is most famous in Brazil. Lesions are most commonly found in the mouth and gastrointestinal tract and in the lymph nodes of the neck.

10. Which of the following disease is an infection of the reticuloendothelial system?
A. Cryptococcosis
B. Moniliasis
C. Histoplasmosis
D. Coccidioidomycosis
Answer: C
Clarification: Histoplasmosis may occur as an acute or chronic, localized or disseminated infection of the reticuloendothelial system.

11. Which of the following does not grow in Sabouraud’s glucose agar media?
A. Histoplasma capsulatum
B. Coccidioides immitis
C. Sporothrix schenckii
D. Blastomyces dermatitidis
Answer: D
Clarification: Blastomyces dermatitidis are large round cells that show optimum growth temperature at 37 degrees C on infusion-blood agar media.

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250+ TOP MCQs on Major Characteristics of Microorganisms and Answers

Microbiology Multiple Choice Questions on “Major Characteristics of Microorganisms”.

1. For the examination of microbial cells we require the use of?
A. High-power microscope
B. Low-power microscope
C. High-power microscope at a magnification of about 1,000 diameters
D. Low-power microscope at a magnification of about 1,000 diameters
Answer: C
Clarification: Microorganisms are very small and their size is usually expressed in micrometers. So for routine examination of microbial cells we require the use of a high-power microscope, usually at a magnification of about 1,000 diameters.

2. Lipopolysaccharide in cell walls is characteristic of?
A. Gram-positive bacteria
B. Gram-negative bacteria
C. Fungi
D. Algae
Answer: B
Clarification: The occurrence of lipopolysaccharide in cell walls is characteristic of Gram-negative bacteria; whereas Gram-positive bacteria have cell walls that contain teichoic acid. Fungal and algal cell walls are very different in composition from those of bacteria.

3. Which microorganism(s) among the following perform photosynthesis by utilizing light?
A. Cyanobacteria
B. Fungi
C. Viruses
D. Cyanobacteria, Fungi and Viruses
Answer: A
Clarification: Cyanobacteria require light as a source of energy to perform photosynthesis. Fungi and viruses are unable to perform photosynthesis and are heterotrophic.

4. Growth of microbes in a solid media is identified by the formation of?
A. pellicle at the top of media
B. colonies
C. sediment at the bottom
D. turbidity
Answer: B
Clarification: On solid media, microbes grow as colonies – distinct, compact masses of cells that are macroscopically visible. When microbes grow in liquid media, the media becomes turbid and growth may either occur only as sediment at the bottom or only as a thin film or pellicle at the top.

5. Which among the following are produced by microorganisms?
A. Fermented dairy products
B. Breads
C. Alcoholic beverages
D. Fermented dairy products, breads and alcoholic beverages
Answer: D
Clarification: Microorganisms are used in many industries for the production of food we eat, like fermented dairy products (sour cream, yogurt), as well as fermented foods as pickles, breads and alcoholic beverages.

6. What are the blood serum proteins produced by animals called?
A. Enzymes
B. Antibodies
C. Amino acids
D. Toxins
Answer: B
Clarification: Certain chemical compounds of microbial cells are called antigens. If microbial cells enter the animal body, the animal responds to these antigens by forming specific blood serum proteins called antibodies, which bind to the antigens.

7. The DNA molecule of microorganisms is made up of base pairs of ________________
A. guanine-cytosine
B. adenine-thymine
C. adenine-cytosine
D. guanine-cytosine and adenine-thymine
Answer: D
Clarification: The DNA molecule has a base composition of the following sequence as base pairs; guanine-cytosine and adenine-thymine. The ratio of A:T= the ratio of G:C.

8. The DNA of Klebsiella pneumonia has a moles % G+C content of?
A. 70-71
B. 50-53
C. 56-58
D. 32-35
Answer: C
Clarification: The sequence of nucleotide bases in the DNA is unique for each kind of microorganism.

Species Moles % G+C content of DNA
Klebsiella pneumonia 56-58
Azospirillum brasilense 70-71
Campylobacter fetus 32-35
Neisseria gonorrhoeae 50-53

9. Plamids are circular DNA molecules capable of autonomous replication.
A. True
B. False
Answer: A
Clarification: In addition to chromosomal DNA, plasmid DNA may sometimes be present in microbial cells. Plasmids are circular DNA molecules that are capable of autonomous replication within bacterial cells that contain them and their presence can confer special characteristics on the cells that contain them.

10. Bdellovibrios come under which group of microorganisms?
A. Viruses
B. Bacteria
C. Fungi
D. Algae
Answer: B
Clarification: Bdellovibrios are bacteria that are predatory on other bacteria. They have the ability to cause diseases or are pathogenic for other microorganisms.

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250+ TOP MCQs on Pure Cultures and Answers

Microbiology Multiple Choice Questions on “Pure Cultures”.

1. Roll-tube technique is used to isolate ___________
A. aerobes
B. anaerobes
C. facultatives
D. stringent anaerobes
Answer: D
Clarification: Roll-tube technique which is a modification of streak-plate technique is used to isolate stringent anaerobes.

2. In pour-plate method, the medium should be maintained at what temperature?
A. 37 degree C
B. 67 degree C
C. 45 degree C
D. 0 degree C
Answer: C
Clarification: In pour plate method, the medium is maintained in a liquid state at a temperature of 45 degrees C to allow thorough distribution of inoculum.

3. Which of the following method can be used to determine the number of bacteria quantitatively?
A. Streak-plate
B. Spread-plate
C. Pour plate
D. Pour-plate and spread plate
Answer: D
Clarification: Due to a higher degree of dilution, pour-plate and spread-plate techniques may be performed in a quantitative manner to determine the number of bacteria present in a specimen.

4. Dilution of the mixed culture is a common step in all the three methods: the streak-plate, the spread-plate and the pour-plate technique.
A. True
B. False
Answer: B
Clarification: The streak-plate technique does not require dilution as a portion of the mixed culture is placed on the surface of an agar medium and streaked across the surface.

5. Which of the following are not performed in lyophilization?
A. agar slant is covered with mineral oil
B. cell suspension is frozen at -60 degree to -78 degree C
C. vials are connected to high-vacuum line
D. bacterial sample is dehydrated
Answer: A
Clarification: In lyophilization or freeze-drying, a dense cell suspension is placed in small vials and frozen at -60 degree to -78 degree C. The vials are then connected to a high-vacuum line. The ice present in the frozen suspension sublimes under the vacuum and results in dehydration of the bacteria.

6. Which of the following is a function of cryoprotective agents?
A. for long-term preservation of cultures
B. prevents cell damage due to ice crystal formation
C. prevents formation of ice
D. to trap the liquid nitrogen
Answer: B
Clarification: For preservation at low temperatures the cells are prepared as a dense suspension in a medium containing cryoprotective agents such as glycerol or dimethyl sulphoxide which prevents cell damage due to ice crystal formation.

7. What is the temperature of liquid nitrogen?
A. -120 degree C
B. 0 degree C
C. -150 degree C
D. -196 degree C
Answer: D
Clarification: Liquid nitrogen has a temperature of -196 degree C and is used for the storage of culture medium.

8. Nichrome loop wire is used in which of the following techniques?
A. Pour-plate
B. Streak-plate
C. Spread-plate
D. Roll-tube technique
Answer: B
Clarification: In the streak plate technique, with the help of a nichrome loop wire, a portion of mixed culture is placed on the surface of an agar medium and streaked across the surface.

9. Which device is used to pick a single bacterial cell from a mixed culture?
A. microscope
B. micropipette
C. microprobe
D. micromanipulator
Answer: D
Clarification: A device called the micromanipulator can be used in conjunction with a microscope to pick a single bacterial cell from a mixed culture. The micro manipulator permits the operator to control the movements of a micropipette or a microprobe so that a single cell can be isolated.

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250+ TOP MCQs on World of Bacteria I – Mycoplasmas and Answers

Microbiology Multiple Choice Questions 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
Answer: B
Clarification: 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.
A. True
B. False
Answer: B
Clarification: 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
D. microaerophiles
Answer: C
Clarification: 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
Clarification: 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?
A. colourless
B. coloured
C. lawn formation
D. fried-egg
Answer: D
Clarification: 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?
A. Nitrogen
B. Carbon
C. Cholesterol
D. Glucose
Answer: C
Clarification: 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?
A. Mycoplasmataceae
B. Acholeplasmataceae
C. Spiroplamataceae
D. Anaplasmataceae
Answer: C
Clarification: 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 __________________
A. bacteria
B. fungi
C. viruses
D. protozoa
Answer: D
Clarification: Lyticum flagellatum is an endosymbiont carried by certain strains of the protozoan Paramecium tetraurelia.

9. L.flagellatum performs the function of synthesizing _______________
A. vitamins
B. hormones
C. organic acids
D. folic acid and toxins
Answer: D
Clarification: 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.
A. True
B. False
Answer: A
Clarification: 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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250+ TOP MCQs on Viruses of Bacteria – Morphology and Structure of Phages and Answers

Microbiology Multiple Choice Questions on “Viruses of Bacteria – Morphology and Structure of Phages”.

1. The nucleic acid core of phages is covered by a protein coat known as _______________
A. capsomere
B. capsid
C. outer envelope
D. nuclear membrane
Answer: B
Clarification: 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
Clarification: The most complex type has a hexagonal head, a rigid tail with a contractile sheath, and tail fibers.

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
Clarification: Bacteriophage MV-L2 has a filamentous form. This type is found in some plant viruses.

4. Pleomorphic viruses possess double-stranded DNA.
A. True
B. False
Answer: A
Clarification: 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
B. polyhedra
C. rod-shaped
D. icosahedral
Answer: C
Clarification: 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?
A. M13
B. T4
C. T7
D. MV-L2
Answer: B
Clarification: 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.
A. True
B. False
Answer: B
Clarification: 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?
A. Pedoviridae
B. Microviridae
C. Styloviridae
D. Corticoviridae
Answer: C
Explanation:Styloviridae is a family of lambda phage viruses that are non-enveloped and has dsDNA.

9. Which of the following coliphage has tadpole shape?
A. T1
B. T4
C. T5
D. T7
Answer: D
Clarification: 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?
A. f1
B. T3
C. f1 and fd
D. T3 and T7
Answer: C
Clarification: Filamentous phages of E.coli include f1 and fd bacteriophages. They all have circular single-stranded DNA.

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250+ TOP MCQs on Soil Microbiology – Nitrogen Cycle and Answers

Microbiology Multiple Choice Questions on “Soil Microbiology – Nitrogen Cycle”.

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
Clarification: 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.
A. True
B. False
Answer: A
Clarification: 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 require 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
Clarification: For the 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.
A. True
B. False
Answer: B
Clarification: Nitrosococcus nitrosus is a type of ammonia-oxidizing bacteria. They usually have an extensive membrane system within their cytoplasm and frequently form 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
Clarification: 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?
A. Ammonification
B. Nitrification
C. Reduction of nitrate to ammonia
D. Denitrification
Answer: D
Clarification: 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
Clarification: The process of denitrification is enhanced in soils by the presence of abundance of organic matter, by elevated temperatures, by neutral or alkaline pH. The 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
Clarification: 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 symbiotic nitrogen fixing bacteria?
A. Rhizobium trifolii
B. Clostridium pasteurianum
C. Azotobacter sp.
D. Escherichia coli
Answer: A
Clarification: Symbiotic nitrogen fixation is accomplished by bacteria of the genus Rhizobium in association with legumes like Rhizobium trifolii.

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