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Interview MCQ Set 1

1. The association which involves the exchange of nutrients between two species is referred to as ______________
a) mutualism
b) syntrophism
c) commensalism
d) antagonism

View Answer

Answer: b [Reason:] 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

View Answer

Answer: c [Reason:] 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

View Answer

Answer: a [Reason:] 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

View Answer

Answer: d [Reason:] 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

View Answer

Answer: a [Reason:] 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

View Answer

Answer: c [Reason:] 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

View Answer

Answer: b [Reason:] Parasitism is defined as a relationship between organisms in which one organism lives in or on another organism referred to as host.

8. The dominant mineral particles in most soils are compounds of _____________
a) sodium
b) potassium
c) magnesium
d) iron

View Answer

Answer: d [Reason:] 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

View Answer

Answer: b [Reason:] 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

View Answer

Answer: c [Reason:] Cyanobacteria, the oxygenic photosynthetic bacteria, are known to grow on the surfaces of freshly exposed rocks where the accumulation of their cells results in simultaneous deposition of organic matter.

Interview MCQ Set 2

1. Which part of the compound microscope helps in gathering and focusing light rays on the specimen to be viewed?
a) Eyepiece lens
b) Objective lens
c) Condenser lens
d) Magnifying lens

View Answer

Answer: c [Reason:] Compound microscope contains three separate lens systems. The condenser lens is placed between the light source and the specimen and it gathers and focuses the light rays in the plane of the microscopic field to view the specimen.

2. What is the minimum distance for the eye to focus any object?
a) 11 cm
b) 25 cm
c) 32 cm
d) 4 2 cm

View Answer

Answer: b [Reason:] The eye cannot focus on objects brought closer to it less than 25 cm; this is, accordingly the distance of maximal effective magnification. An object must also subtend an angle at the eye of 1 degree or greater.

3. Resolving power of a microscope is a function of____________
a) Wavelength of light used
b) Numerical aperture of lens system
c) Refractive index
d) Wavelength of light used and numerical aperture of lens system

View Answer

Answer: d [Reason:] The ability of a microscope to distinguish two adjacent points as distinct and separate is known as resolving power. Resolving power is a function of wavelength of light used and the numerical aperture (NA) of the lens system.NA refers to the refractive index of the medium multiplied with the sine value of the half-aperture angle.

4. The greatest resolution in light microscopy can be obtained with ___________
a) Longest wavelength of visible light used
b) An objective with minimum numerical aperture
c) Shortest wavelength of visible light used
d) Shortest wavelength of visible light used and an objective with the maximum numerical aperture

View Answer

Answer: d [Reason:] The relationship between numerical aperture (NA) and resolution is:- Resolution (d) = wavelength / 2(NA) Thus maximum resolution is obtained with the shortest wavelength of visible light and an objective with the maximum NA.

5. Oil immersion objective lens has an NA value of____________
a) 0.65
b) 0.85
c) 1.33
d) 1.00

View Answer

Answer: c [Reason:] NA = refractive index * sine (half-aperture angle). The maximum NA for a dry objective is less than 1.0 as the refractive index of air is 1.The values of NA for oil immersion lens is slightly greater than 1.0 in the range of (1.2 to 1.4) as the refractive index of oil is 1.56.

6. In fluorescence microscopy, which of the following performs the function of removing all light except the blue light?
a) Exciter filter
b) Barrier filter
c) Dichroic mirror
d) Mercury arc lamp

View Answer

Answer: a [Reason:] In fluorescence microscopy, the function of the exciter filter is to remove all but the blue light; the barrier filter blocks out blue light and allows any other light emitted by the fluorescing specimen to pass through and reach the eye.

7. Total Magnification is obtained by__________
a) Magnifying power of the objective lens
b) Magnifying power of eyepiece
c) Magnifying power of condenser lens
d) Magnifying power of both the objective lens and eyepiece

View Answer

Answer: d [Reason:] The total magnification is determined by multiplying the magnifying power of the objective by that of the eyepiece. Generally, an eyepiece having a magnification of 10X is used although eyepieces of higher or lower magnifications are available.

8. In light microscopy, which of the following is used as fixatives prior to staining technique?
a) Osmic acid
b) Glutaraldehyde
c) Heat
d) Osmic acid, glutaraldehyde, heat

View Answer

Answer: c [Reason:] Most staining techniques kill cells and so preliminary to staining, the cells are sometimes fixed. Commonly used chemical fixatives include osmic acid and mainly glutaraldehyde. But for light microscopy heat is the most commonly used fixative.

9. In Phase contrast microscopy, the rate at which light enters through objects is__________
a) Constant
b) Inversely proportional to their refractive indices
c) Directly proportional to their refractive indices
d) Exponentially related to their refractive indices

View Answer

Answer: b [Reason:] Phase contrast microscopy is based on the fact that the rate at which light travels through objects is inversely related to their refractive indices. Since the frequency of light waves is independent of the medium through which they travel, the phase of a light ray passing through an object of higher refractive index than the surrounding medium will be relatively retarded.

10. Which part of the light microscope controls the intensity of light entering the viewing area?
a) Coarse adjustment screw
b) Fine adjustment screw
c) Diaphragm
d) Condenser lens

View Answer

Answer: c [Reason:] On the condenser is mounted a shutter like apparatus called the diaphragm which opens and closes to permit more or less light into the viewing area. Condenser lens just helps in condensing the light rays. Coarse and fine adjustment screws are used for focusing under different power lens.

Interview MCQ Set 3

1. What does a viral DNA becomes after being associated with the bacterial chromosome?
a) gene
b) prophage
c) plasmid
d) plaque

View Answer

Answer: b [Reason:] In lysogeny the viral DNA of the temperate phage, instead of taking over the functions of the cell’s genes, is incorporated into the host DNA and becomes a prophage in the bacterial chromosome, acting as a gene.

2. In which of the following method, the viral particles are transmitted through lysis of cell?
a) Lytic cycle
b) Lysogeny
c) Replication
d) Translation

View Answer

Answer: a [Reason:] In the lytic cycle after the infection of bacterial cells by phages, the viral particles are transmitted through lysis of cell and finally terminates.

3. epressor protein makes the cell resistant to lysis.
a) True
b) False

View Answer

Answer: a [Reason:] The temperate phage possesses a gene that codes for a repressor protein which makes the cell resistant to lysis initiated either by the prophage or by lytic infection by other viruses. The multiplication of the phage is repressed and lysogenization occurs.

4. Which of the following is the characteristic of repressor protein?
a) basic protein
b) acidic protein
c) basic protein,molecular weight of 26000
d) acidic protein,molecular weight of 26000

View Answer

Answer: d [Reason:] The repressor protein is an acidic protein with a molecular weight of 26000.It has been isolated from lambda phage and purified.

5. cro gene is an example of immunity repressor.
a) True
b) False

View Answer

Answer: b [Reason:] Upon infection by lambda phage, the phage cro gene is transcribed, resulting in the synthesis of a protein repressor that inhibits the synthesis of the immunity repressor.

6. Which of the following gene codes for an enzyme which directs the insertion of the phage DNA into the bacterial chromosome?
a) recA gene
b) cro gene
c) int gene
d) gal gene

View Answer

Answer: c [Reason:] A lambda phage enzyme,coded by the int gene, directs the insertion of the phage DNA into the bacterial chromosome.It catalyzes a single site-specific recombination event, resulting in the insertion of the phage DNA into the cell genome.

7. Which of the following phage do not cause lysogeny?
a) T2
b) T1
c) lambda
d) P1

View Answer

Answer: a [Reason:] Phages like T2 that do not cause lysogeny are termed virulent.Phages produced by lysogenic strains are termed temperate phages, and the relationship between the phage and the bacterium is termed lysogeny.

8. The protein integrase is encoded by which of the following gene?
a) gal gene
b) lambda gene
c) bio gene
d) cro gene

View Answer

Answer: b [Reason:] Integration of the lambda chromosome requires the action of a protein termed integrase encoded by a lambda gene and occurs at a 13 base pair region of DNA sequence homology between the bacterial and phage chromosomes.

9. In which of the following phage prophage exists as a circular form?
a) Phage lambda type
b) Phage P1 type
c) Phage T2 type
d) Phage T1 type

View Answer

Answer: b [Reason:] In lysogeny of the P1 type, viral DNA does not normally become integrated into the host chromosome. Instead the prophage exists as a circular, self-replicating, double-stranded DNA element termed a plasmid.

Interview MCQ Set 4

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

View Answer

Answer: c [Reason:] 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

View Answer

Answer: b [Reason:] 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

View Answer

Answer: a [Reason:] 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

View Answer

Answer: b [Reason:] On solid media, microbes grow as colonies – distinct, compact masses of cells that are macroscopically visible. When microbes grow in a 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

View Answer

Answer: d [Reason:] 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

View Answer

Answer: b [Reason:] 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

View Answer

Answer: d [Reason:] 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

View Answer

Answer: c [Reason:] The sequence of nucleotide bases in the DNA is unique for each kind of microorganism.

SpeciesMoles % G+C content of DNA
Klebsiella pneumonia56-58
Azospirillum brasilense70-71
Campylobacter fetus32-35
Neisseria gonorrhoeae50-53

9. Plamids are circular DNA molecules capable of autonomous replication.
a) True
b) False

View Answer

Answer: a [Reason:] 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

View Answer

Answer: b [Reason:] Bdellovibrios are bacteria which are predatory on other bacteria. They have the ability to cause diseases or are pathogenic for other microorganisms.

Interview MCQ Set 5

1. How much percentage of aqueous solution of phenol rapidly kills the vegetative cells of microorganisms?
a) 1%
b) 2%
c) 5%
d) 10%

View Answer

Answer: c [Reason:] Phenol is a very effective disinfectant.A 5% aqueous solution of phenol rapidly kills the vegetative cells of microorganisms; spores are much more resistant.

2. The antimicrobial activity of phenolics is not reduced at which of the following conditions?
a) acidic pH
b) alkaline pH
c) low temperatures
d) presence of soap

View Answer

Answer: d [Reason:] The antimicrobial activity of phenolics is reduced at an alakaline pH and by organic material.Low temperaturs and the presence of soap also reduce antimicrobial activity.

3. Alcohol concentrations above 60% are effective against _________________
a) bacteria
b) fungi
c) germs
d) viruses

View Answer

Answer: d [Reason:] Alcohol concentrations above 60% are effective against viruses; however the effectiveness is influenced considerably by the amount of extraneous proteinmaterial in the mixture.The extraneous protein reacts with the alcohol and thus protects the virus.

4. Polyvinylpyrrolidone (PVP) is a complex belonging to which group?
a) Phenolic compounds
b) Iodophors
c) Metals
d) Aldehyde

View Answer

Answer: b [Reason:] Polyvinylpyrrolidone (PVP) is a complex belonging to iodophors.Iodophors are mixtures of iodine with surface-active agents which act as carriers and solubilizers for the iodine.They possess the germicidal characteristics of iodine.

5. Which of the following agents irreversibly oxidize and inactivate proteins with sulphydral groups?
a) Alcohol
b) Phenol
c) Iodine
d) Chlorine

View Answer

Answer: c [Reason:] Iodine is an oxidizing agent and oxidizing agents can irreversibly oxidize and thus inactivate essential metabolic compounds such as proteins with sulphydral groups.

6. Chlorinated lime is the alternative name for __________________
a) Calcium hypochlorite
b) Sodium hypochlorite
c) Chloramine-T
d) Azochloramide

View Answer

Answer: a [Reason:] Calcium hypochlorite, Ca(OCl)2 is also known as chlorinated lime and it acts as an effective disinfectant like free chlorine.

7. Chloramines are more stable than than hypochlorites.
a) True
b) False

View Answer

Answer: a [Reason:] One of the advantage of chloramines is stability; they are more stable than the hypochlorites in terms of prolonged release of chlorine.

8. Solutions of sodium hypochlorite of a 1% concentration are used for ________
a) sanitizing dairy equipments
b) personal hygiene and a household disinfectant
c) household bleaches
d) disinfecting open wounds

View Answer

Answer: b [Reason:]Solutions of sodium hypochlorite of a 1% concentration are used for personal hygiene and as a household disinfectant and higher concentrations of 5-12% are also employed as household bleaches.

9. Which among the following is an example of organic compound of mercury?
a) Mercuric chloride
b) Mercuric oxide
c) Mercurochrome
d) Ammoniated mercury

View Answer

Answer: c Example: Mercurochrome is an organic compound of mercury which are less irritating and less toxic than the inorganic mercury compounds.They are employed as antiseptics on cutaneous and mucosal surfaces.

10. Which of the following agents cause death to the cell by coagulation of cytoplasmic proteins?
a) Alcohol
b) Dyes
c) Chlorine
d) Heavy metals

View Answer

Answer: d [Reason:] High concentration of salts of heavy metals like mercury,silver, and copper coagulate cytoplasmic proteins resulting in damage or death to the cell.Salts of heavy metals are also precipitants and in high concentration they cause death of cell.

11. Gram-negative organisms are more susceptible to higher concentrations of triphenylmethane dyes.
a) True
b) False

View Answer

Answer: a [Reason:] Gram-positive organisms are more susceptible to lower concentrations of triphenylmethane dyes than are Gram-negative ones.

12. Which of the following is an acridine dye?
a) crystal violet
b) malachite green
c) tryptoflavine
d) brilliant green

View Answer

Answer: c [Reason:] Two examples of dyes derived from acridine are acriflavine and tryptoflavine.These compounds exhibit selective inhibition against bacteria,particularly staphylococci and gonococci.

13. Gonococci are inhibited by tryptoflavine in dilutions of ____________________
a) 1:200,000
b) 1:300,000
c) 1:1,000,000
d) 1:10,000,000

View Answer

Answer: d [Reason:] Gonococci are inhibited by tryptoflavine in dilutions of 1:10,000,000 to 1:50,000,000.They possess little,if any, antifungal activity.

14. Ceepryn belongs to which of the following categories?
a) Anionic detergents
b) Cationic detergents
c) Nonionic detergents
d) Ammonium salts

View Answer

Answer: b [Reason:] Those which ionize with the detergent property resident in the cation are referred as cationic detergents.An example of this is Ceepryn which is Cetylpyridinium chloride.

15. Which of the following agents are used as a preservative in ophthalmic solutions?
a) alcohol
b) quaternary ammonium salts
c) phenol
d) aldehydes

View Answer

Answer:b [Reason:] The combined properties of germicidal activity and low toxicity,high solubility in water, stability in solution, and non-corrosiveness have resulted in many applications of quaterneries as disinfectants and sanitizing agents.They are used as skin disinfectants, as a preservative of ophthalmic solutions etc.