Category: MICROBIOLOGY Objective Questions

Microbiology Multiple Choice Questions on “Pure Cultures and Cultural Characteristics – Selective Methods”.

1. Isolation of pure culture refers to ___________
A. purification of culture
B. introduction of inoculum
C. separation of a single colony
D. to grow microorganisms on a surface
Answer: C
Clarification: To study the characteristics of one species, that species must be separated from all the other colonies of species, i.e., it must be isolated in pure culture.

2. Enrichment media allows the growth of a large number of varied bacterial species.
a)True
B. False
Answer: B
Clarification: Enrichment media is a selective method used for the enhancement of the growth of a particular bacterial species.

3. Which of the following is not a physical method for selection of pure culture?
A. Heat treatment
B. pH of the media
C. Cell size and motility
D. Use of dilute media
Answer: D
Clarification: Use of dilute media is a chemical method of selection in which a mixed culture was inoculated into a very dilute medium to isolate a particular bacterial colony.

4. In physical method of selection, endospore-forming bacteria can be obtained by heating the mixed culture to _____________
A. 70 degree C for 10 minutes
B. 80 degree C for 10 minutes
C. 60 degree C for 10 minutes
D. 90 degree C for 10 minutes
Answer: B
Clarification: To select for endospore-forming bacteria, a mixed culture can be heated to 80 degrees C for 10 minutes before being used to inoculate culture media. Vegetative cells will be killed by this treatment but endospores will survive and subsequently germinate and grow.

5. Vibrio cholerae can grow in a medium with a pH of _______
A. 5.5
B. 7.0
C. 8.5
D. 2.0
Answer: C
Clarification: Vibrio cholerae, cholera causing bacterium can be selected from a medium with a ph of 8.5; most intestinal bacteria are unable to grow at this pH.

6. Disease-producing species occurring in a mixed culture can be selected by taking advantage of _________
A. its pathogenic properties
B. special carbon source
C. special nitrogen source
D. toxic chemicals
Answer: A
Clarification: In the biological method of selection, a disease producing species occurring in a mixed culture can often be selected by taking advantage of its pathogenic properties. Others are chemical methods of selection.

7. Treponema sp. can be selected by taking advantage of ____________
A. small cell size
B. motility
C. dilute media
D. small cell diameter and bacterial motility
Answer: D
Clarification: Treponema sp. from the human oral cavity can be selected by taking advantage of its small diameter and bacterial motility. They have the ability to swim through solid agar media.

8. A large cluster of colonies are obtained in streak plate method.
A. True
B. False
Answer: B
Clarification: In streak plate method, the bacterial cells are thinned out so that the bacterial cells are far apart in the medium to ensure that colony developing from one cell does not merge with that growing from another.

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Microbiology Multiple Choice Questions on “World of Bacteria I – Rickettsias and Chlamydias”.

1. Which of the following infect arthropods only?
A. Rickettsieae
B. Ehrlichieae
C. Wolbachieae
D. Rochalimaea
Answer: C
Clarification: The Wolbachieae are not pathogenic for vertebrates, they infect arthropods only.

2. The Rickettsias and Chlamydias are similar in all respects.
A. True
B. False
Answer: B
Clarification: The Rickettsias synthesize ATP as a source of energy whereas Chlamydias cannot synthesize ATP.

3. Classical typhus fever is transmitted by which of the following arthropod?
A. ticks
B. mites
C. fleas
D. lice
Answer: D
Clarification: Classical typhus fever is caused by Rickettsia species and the arthropod vector which transmits the disease is lice.

4.”Growing epicellularly” means ______________
A. on the surface of host cells
B. within the host cell
C. engulfing the host cell
D. damaging the cell membrane of host cell
Answer: A
Clarification: Growing epicellularly means growing on the surface of host cells. Rochalimaea grow epicellularly rather than in the cytoplasm or nucleus.

5. Which of the following genus of Rickettsiaceae have a high resistance to heat?
A. Rickettsia
B. Rochalimaea
C. Coxiella
D. Wolinella
Answer: C
Clarification: The organisms belonging to Coxiella have an unusually high resistance to heat [may survive a temperature of 62 degree C for 30 mins], probably due to the occurrence of endospore-like structures in the cells.

6. C.burnetti causes which of the following diseases?
A. Q fever
B. Trench fever
C. Rocky Mountain spotted fever
D. Typhoid
Answer: A
Clarification: C.burnetti is the causative agent of the Q fever, a type of pneumonia. It belongs to the family Rickettsiaceae.

7. Biting flies occur in which of the following place?
A. Australia
B. North America
C. South America
D. Africa
Answer: C
Clarification: Biting flies occur along the western slopes of the Andes mountains in South America. They transmit Oroya fever in humans.

8. Initial body in the reproduction of Chlamydias is larger than the elementary body.
A. True
B. False
Answer: A
Clarification: Within the vacuole the elementary body is reorganized into a reticulate body known as the initial body, which is two or three times the size of the elementary body and contains a less dense arrangement of nucleoid material.

9. Which is the most prevalent sexually transmitted disease in the US?
A. Syphilis
B. AIDS
C. Lymphogranuloma venerum
D. Nongonococcal urethritis
Answer: D
Clarification: Nongonococcal urethritis is the most prevalent sexually transmitted disease in the United States and is caused by the organisms belonging to the genus Chlamydia.

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Microbiology Quiz focuses on “Characteristics of Some Major Groups of Protozoa”.

1. Members of order Diplomonadida have how many flagella?
A. 2 to 4
B. 6 to 8
C. 2 to 8
D. 1 to 2
Answer: B
Clarification: Members of the order Diplomonadida have bilateral symmetry and 6 to 8 flagella.

2. Trypanosoma belongs to which of the following order?
A. Kinetoplastida
B. Retortamonadida
C. Choanoflagellida
D. Trichomonadida
Answer: A
Clarification: Trypanosoma belongs to the order Kinetoplastida which are grouped with other organisms due to the presence of kinetoplast (an extracellular region of DNA associated with the mitochondrion).

3. The Trichomonads found in the intestine are ___________________
A. Trichomonas buccalis
B. Trichomonas hominis
C. Trichomonas vaginalis
D. Trichonympha campanula
Answer: B
Clarification: Trichomonas hominis are found in the intestine where they may be associated with diarrheal conditions.

4. African sleeping sickness is transmitted by which of the following agents?
A. biting insects
B. sexual means
C. tsetse fly
D. bloodsucking insects
Answer: C
Clarification: Trypanosoma rhodesiense are transmitted by the tsetse fly and causes African sleeping sickness.

5. Amoebas carry on a special kind of respiration in the form of exchange of gases between the cell and the surrounding field.
A. True
B. False
Answer: A
Clarification: Amoebas carry on a special kind of respiration in the form of an exchange of gases between the cell and the surrounding fluid, for at rather regular intervals vacuoles apparently containing some carbon dioxide in solution are expelled from the cell through an opening that develops in the cell membrane.

6. Which of the following protozoa construct shells of silica?
A. foraminiferans
B. radiolarians
C. heliozoida
D. sporozoa
Answer: B
Clarification: Radiolarians, like foraminiferans, are marine forms, but most of them construct shells of silica. Deposits of their skeletons are incorporated in rocks formed in areas where they have occurred in abundance.

7. The Sporozoa belongs to which of the following phylum?
A. Ciliophora
B. Labyrinthomorpha
C. Microspora
D. Apicomplexa
Answer: D
Clarification: The Sporozoa belongs to the phylum Apicomplexa. All sporozoa are parasitic for one or more animal species.

8. What is the shape of Paramecium?
A. circular
B. slipper-like
C. spindle shaped
D. irregular
Answer: B
Clarification: Paramecia are easily distinguished by their characteristic shape, which has been likened to that of slipper. The anterior end of the cell is rounded and the posterior end is slightly pointed giving it a slipper-like shape.

9. Undigested particles are eliminated from the cell through the ___________________
A. gullet
B. contractile vacuole
C. cytoproct
D. cell membrane
Answer: C
Clarification: In Paramecium the undigested particles are eliminated from the cell through the cytoproct. Waste fluids are collected in the contractile vacuoles.

10. During binary fission in Paramecium, the rear daughter cell receives a new gullet?
A. True
B. False
Answer: B
Clarification: Paramecia reproduce asexually by binary fission in which the rear daughter cell receives the gullet of the parent, and a new gullet is formed for the other new cell.

11. Which of the following comprises large cone-shaped protozoa?
A. Didinium
B. Vorticella
C. Stentor
D. Colpoda
Answer: C
Clarification: The genus Stentor comprises large cone-shaped protozoa that move about freely but attach to some object by a tapered lower end while feeding.

To practice all areas of Microbiology for Quizzes, .

Microbiology Multiple Choice Questions on “Interactions among Soil Microorganisms”.

1. The association which involves the exchange of nutrients between two species is referred to as ______________
A. mutualism
B. syntrophism
C. commensalism
D. antagonism
Answer: B
Clarification: Syntrophism is a mutualistic association that involves the exchange of nutrients between two species.

2. The degradation of complex molecules in soil by fungi for utilization by bacteria is an example of which type of association?
A. Neutralism
B. Mutualism
C. Commensalism
D. Antagonism
Answer: C
Clarification: Many bacteria are unable to utilize cellulose, but they can and do utilize the fungal breakdown products of cellulose e.g., glucose and organic acids. This phenomenon is referred to as commensalism.

3. Which of the following types of association is present among Staphylococcus aureus and Aspergillus terreous?
A. antagonism
B. mutualism
C. parasitism
D. commensalism
Answer: A
Clarification: Staphylococcus aureus produces a diffusable antifungal material that causes distortions and hyphal swellings in Aspergillus terreous. This is an antagonistic relationship between these two organisms.

4. Lytic enzymes which destroy are secreted by which of the following microorganism?
A. fungi
B. algae
C. staphylococcus
D. myxobacteria
Answer: D
Clarification: Myxobacteria (slime bacteriA. and streptomycetes are antagonistic because they secrete potent lytic enzymes which destroy other cells by digesting their cell wall or other protective surface layers.

5. Fungi produces which of the following inhibitory toxic product?
A. cyanide
B. fatty acids
C. methane
D. sulphides
Answer: A
Clarification: Cyanide is produced by certain fungi in concentrations toxic to other microorganisms.

6. Which of the following comes under the category of positive association?
A. neutralism
B. parasitism
C. commensalism
D. ammensalism
Answer: C
Clarification: The phenomenon of commensalism is a positive type of association because it refers to a relationship between organisms in which one species of a pair benefits, the other is not affected.

7. Parasitism results from competition among organisms for essential nutrients.
A. True
B. False
Answer: B
Clarification: Parasitism is defined as a relationship between organisms in which one organism lives in or on another organism referred to as a host.

8. The dominant mineral particles in most soils are compounds of _____________
A. sodium
B. potassium
C. magnesium
D. iron
Answer: D
Clarification: The dominant mineral particles in most soils are compounds of silicon, aluminum, iron and lesser amounts of other minerals, including calcium, magnesium, potassium, sodium, nitrogen etc.

9. Bacteria are likely to be more prevalent in soils of vineyards, orchards and apiaries.
A. True
B. False
Answer: B
Clarification: Yeasts are likely to be more prevalent in soils of vineyards, orchards, and apiaries, where special conditions, particularly the presence of sugars favor their growth.

10. Which of the following organisms are known to grow on the surfaces of freshly exposed rocks?
A. green algae
B. diatoms
C. cyanobacteria
D. yeast
Answer: C
Clarification: Cyanobacteria, the oxygenic photosynthetic bacteria, are known to grow on the surfaces of freshly exposed rocks where the accumulation of their cells results in the simultaneous deposition of organic matter.

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Microbiology Multiple Choice Questions on “Genotypic Changes”.

1. Bacterial chromosome has the capacity to code for ____________ different proteins.
A. 900
B. 300
C. 1500
D. 3500
Answer: D
Clarification: It has been estimated that bacterial chromosomes have the capacity to code for approximately 3500 different proteins.

2. Which is the functional unit of inheritance?
A. DNA
B. Chromosome
C. Gene
D. RNA
Answer: C
Clarification: A gene is a functional unit of inheritance; it specifies the formation of a particular polypeptide as well as various types of RNA. The chromosome is divided into genes.

3. Populations of cells descending from a single cell are known as ____________
A. mutants
B. clones
C. wild-type cells
D. parent cell
Answer: B
Clarification: Populations of cells descending from a single cell are known as clones but a cell or an organism which shows the effects of a mutation is called a mutant.

4. The replacement of a purine by a pyrimidine or vice versa is known as ____________
A. tranversion
B. transition
C. base-pair substitution
D. missense mutation
Answer: A
Clarification: Transversion is a type of point mutation is the replacement of a purine by a pyrimi-dine or vice versa.

5. Sickle cell anemia is which type of mutation?
A. nonsense mutation
B. missense mutation
C. deletion mutation
D. insertion mutation
Answer: B
Clarification: A good example of a missense mutation in humans is the disease sickle cell anemia. A single base substitution in the codon for the sixth amino acid of normal hemoglobin A changes the sixth amino acid from glutamic acid to valine, thus forming the characteristic hemoglobin S of sickle cell anemia.

6. In nonsense mutation, the new mRNA codon specifies the same amino acid as that from the original codon.
A. True
B. False
Answer: B
Clarification: In neutral mutation the altered gene triplet produces a mRNA codon that specifies the same amino acid because the codon resulting from mutation is a synonym for the original codon.

7. Which of the following mutations result in frameshift mutation?
A. missense mutation
B. transition
C. transversion
D. insertion
Answer: D
Clarification: Insertion and deletion mutations result in a shift of the reading frame caused by the addition or loss of one or more nucleotides.

8. Which of the following mutagen causes a break in the phosphodiester backbone of the nucleic acid?
A. UV light
B. X-rays
C. Nitrous acid
D. base analogs
Answer: B
Clarification: When x-rays interact with DNA, the result is usually a break in the phosphodiester backbone of the nucleic acid.

9. Base analogs have the same hydrogen-bonding properties as the normal bases.
A. True
B. False
Answer: B
Clarification: Although similar in structure, base analogs do not have the same hydrogen-bonding properties as the normal bases. They can therefore introduce errors in a replication which results in mutation.

10. Acridine orange is which type of mutagen?
A. base analog
B. chemical compounds
C. intercalating agents
D. transposons
Answer: C
Clarification: Acridine orange is an intercalating agent that can intercalate between the base pairs in the central stack of the DNA helix and distort the structures and cause subsequent replication errors.

11. Photoreactivation can cause repair of DNA damaged by which of the following mutagens?
A. UV rays
B. X-rays
C. Nitrous acid
D. Base analogs
Answer: A
Clarification: Photoreactivation mechanism is used for repairing damage caused by UV radiation.A special enzyme designated PRE, induced by visible light, splits or unlinks the dimers formed because of exposure to UV light and restores the DNA to its original state.

12. Which of the following enzyme is used to join the DNA fragments together?
A. polymerases
B. exonuclease
C. endonuclease
D. ligase
Answer: D
Clarification: Ligase enzyme is used to join the fragments together which are formed by polymerases to fill in the gaps in the DNA strand.

13. What is the mutation rate for E.coli per bacterium per cell division?
A. 5.8 x 10^-6
B. 5.8 x 10^-9
C. 5.8 x 10^-8
D. 5.8 x 10^-7
Answer: C
Clarification: Mutation rate for E.coli maybe given as 5.8 x 10^-8 mutations per bacterium per cell division.

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