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Interview MCQ Set 1

1. The organisms which can use reduced inorganic compounds as electron donors are known
as _________
a) chemotrophs
b) organotrophs
c) lithotrophs
d) phototrophs

View Answer

Answer: c [Reason:] Organisms which can use reduced inorganic compounds as electron donors are termed as lithotrophs. Some organisms which use organic compounds as electron donors are called organotrophs.

2. Which of the following is nutritional characterization of Escherichia coli?
a) Chemotrophic
b) Organotrophic
c) Autotrophic
d) Chemotrophic, Organotrophic, Heterotrophic

View Answer

Answer: d [Reason:] Escherichia coli are chemotrophic, organotrophic, and heterotrophic organism. This means they rely on chemical compounds for their energy and uses organic compounds as electron donors. They also require organic compounds as their carbon source and are hence heterotrophic.

3. Which of the following amino acids require sulphur for their synthesis?
a) tryptophan
b) methionine
c) cystine
d) methionine and cystine

View Answer

Answer: d [Reason:] Sulphur is needed for synthesis of certain amino acids like methionine and cystine. Some bacteria require organic sulphur compounds, some are capable of utilizing inorganic sulphur compounds and some can even use elemental sulphur.

4. Phosphorus is essential component of __________
a) teichoic acid
b) nucleotides
c) phospholipids
d) teichoic acid, nucleotides, phospholipids

View Answer

Answer: d [Reason:] Phosphorus, usually supplied in the form of phosphate,is an essential component of nucleotides,nucleic acids,phospholipids,teichoic acids, and other components.

5. Which of the following are trace elements?
a) Potassium ion
b) Sodium ion
c) Copper ion
d) Magnesium ion

View Answer

Answer: c [Reason:] Trace elements are those elements which are needed at very low concentrations such as Zinc ion, Copper ion, Manganese ion, Nickel ion, Cobalt ion, Boron ion, Molybdenum ion. They always occur as contaminants of other components of culture media in amounts sufficient to support bacterial growth.

6. Which of the following ions are cofactors for various enzymes?
a) Potassium ion
b) Iron ion
c) Magnesium ion and Iron ion
d) Calcium ion

View Answer

Answer: c [Reason:]Among the trace elements, iron ion, magnesium ion, zinc ion, manganese ion and copper ion are known to be cofactors for various enzymes.

7.”Red extreme halophiles”, are members of the archaebacterial which cannot grow with less than 12 to 15 percent NaCl.
a) True
b) False

View Answer

Answer: a [Reason:] Most bacteria do not require Na ion, but certain marine bacteria,cyanobacteria and photosynthetic bacteria do require it. For those members of the archaeobacteria known as the “red extreme halophiles”, the requirement is astonishing: they cannot grow with less than 12 to 15 percent NaCl. They require this high level of NaCl for maintenance of the integrity of their cell walls and for the stability and activity of certain of their enzymes.

8. Which of the following are functions of water in the culture medium?
a) nutrients must be in aqueous solution
b) cofactor of enzymes
c) provides resistance to sudden transient temperature changes
d) it is a chemical reactant, nutrients must also be present in aqueous solution and provides resistance to sudden temperature changes.

View Answer

Answer:d [Reason:] In case of bacteria, all nutrients must be in aqueous solution before they can enter the cells. The high specific heat of water provides resistance to sudden, transient temperature changes in the environment. Water is also a chemical reactant, being required for the many hydrolytic reactions carried out by a cell.

9. Chromatium okenii uses which of the following compound as electron donor?
a) Hydrogen sulphide
b) Fatty acids
c) Alcohol
d) Succinate

View Answer

Answer: a [Reason:] Chromatium okenii are photolithotrophs i.e., they are phototrophic bacteria that uses inorganic compounds as their source of electrons.They use Hydrogen Sulphide as its electron donor,oxidizing it to elemental sulphur.

10.Which of the following bacteria can grow both as chemolithotrophs or as chemoorganotrophs?
a) Nitrosomonas sp.
b) Pseudomonas pseudoflava
c) Rhodospirillum rubrum
d) Chromatium okenii

View Answer

Answer: b [Reason:] Pseudomonas pseudoflava can grow either as chemolithotrophs or chemoorganotrophs. They can use either the organic compound glucose or the inorganic compound hydrogen as its source of electrons.

Interview MCQ Set 2

1. Which of the following viruses are termed as ‘orphan’ viruses?
a) retroviruses
b) echoviruses
c) coxsackieviruses
d) adenoviruses

View Answer

Answer: b [Reason:] 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

View Answer

Answer: b [Reason:] 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

View Answer

Answer: c [Reason:] 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

View Answer

Answer: d [Reason:] 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

View Answer

Answer: c [Reason:] 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

View Answer

Answer: a [Reason:] 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

View Answer

Answer: d [Reason:] 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

View Answer

Answer: c [Reason:] 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

View Answer

Answer: a [Reason:] 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

View Answer

Answer: b [Reason:] 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

View Answer

Answer: b [Reason:] 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

View Answer

Answer: c [Reason:] 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

View Answer

Answer: a [Reason:] 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

View Answer

Answer: b [Reason:] 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.

Interview MCQ Set 3

1. Which of the following forms of water is the most contaminated?
a) Underground water
b) Rainwater
c) Surface water
d) Water stored in ice caps

View Answer

Answer: c [Reason:] Surface water should not be used for drinking purposes unless it is subjected to purification, since there is constant danger of contamination and consequent transmission of disease.

2. Alum is used for which of the following purification process?
a) Sedimentation
b) Filtration
c) Disinfection
d) Ozonation

View Answer

Answer: a [Reason:] Sedimentation is enhanced by addition of alum (aluminum sulphate) at the treatment plant, which produces a sticky flocculent precipitate.

3. The potability of water can be checked by sanitary surveys.
a) True
b) False

View Answer

Answer: b [Reason:] Sanitary surveys reveal whether water is being produced under conditions in which potable water would ordinarily be produced. However, potability can be determined only by chemical and bacteriological laboratory tests.

4. The coliform group of bacteria includes all the __________________ bacilli
a) aerobic
b) anaerobic
c) aerobic,non-sporulating
d) aerobic,Gram-negative,non-sporulating

View Answer

Answer: d [Reason:] The coliform group of bacteria includes all the aerobic and facultatively anaerobic, Gram-negative, non-sporulating bacilli that produce acid and gas from the fermentation of lactose.

5. Which of the following organism does not belong to coliform group of bacteria?
a) Salmonella
b) Serratia
c) Enterobacter
d) Proteus

View Answer

Answer: c [Reason:] Coliform group of bacteria consists of E.coli and Enterobacter aerogenes. All others belong to the enteric group.

6. Coliforms are natural inhabitants of the large intestine of human and animals.
a) True
b) False

View Answer

Answer: a [Reason:] Coliforms, fecal streptococci and Clostridium perfringens are normal inhabitants of the large intestine of humans and other animals and are consequently present in feces.

7. Which of the following acts as a carbon source for Enterobacter aerogenes?
a) Peptone
b) Sodium citrate
c) Yeast extract
d) Tryptone

View Answer

Answer: b [Reason:] Enterobacter aerogenes will grow in a chemically defined medium in which sodium citrate is the only carbon compound as it is capable of utilizing it.

8. What will be the plate count of good quality water?
a) 10 per ml
b) 50 per ml
c) 100 per ml
d) 1000 per ml

View Answer

Answer: c [Reason:] In standard plate count method, water of good quality is expected to give a low count, less than 100 per ml.

9. Among the following which microorganism acts as a representative of fecal streptococci group?
a) Streptococcus faecalis
b) Streptococcus bovis
c) Streptococcus equinus
d) Streptococcus faecium

View Answer

Answer: a [Reason:] Streptococcus faecalis is representative of the fecal streptococci group and are abundantly present in the large intestine of humans.Their occurrence in water is indicative of fecal pollution.

10. Thiobacillus can produce an acidity in the range of pH __________
a) 7
b) 5
c) 3
d) 1

View Answer

Answer: d [Reason:] Organisms of the genus Thiobacillus oxidize elemental sulphur to sulphuric acid and can produce an acidity in the range of pH 1.

11. In which of the following organism does iron secreted to form stalks or ribbons attached to the cell?
a) Sphaerotilus
b) Gallionella
c) Thiobacillus
d) Streptococcus

View Answer

Answer: b [Reason:] Some iron bacteria such as Gallionella transform soluble compounds of iron to insoluble compounds of iron which are secreted to form stalks or ribbons attached to the cell.

Interview MCQ Set 4

1. Which of the following microorganism causes infection in burns?
a) Pseudomonas aeruginosa
b) Clostridium perfringens
c) Borrelia sp
d) Streptococcus sp

View Answer

Answer: a [Reason:] Burns often become infected by Pseudomonas aeruginosa or other aerobic or facultatively anaerobic bacteria from the surrounding.

2. V. cholerae does not penetrate into the body.
a) True
b) False

View Answer

Answer: a [Reason:] V. cholerae, the causative agent of cholera, multiplies on the epithelial layer of the small intestine where it produces a toxin that causes the loss of fluid from the epithelial cells and kills the cells.

3. Which of the following microorganism causes relapsing fever in humans?
a) Pseudomonas aeruginosa
b) Clostridium perfringens
c) Borrelia sp.
d) Streptococcus sp.

View Answer

Answer: c [Reason:] Borrelia sp. cause relapsing fever in humans when the spirochetes are introduced through the bite of a tick or a body louse.

4. Which of the following microorganism participates in active penetration into the body?
a) Clostridium perfringens
b) Shigella
c) Borrelia sp.
d) Pseudomonas aeruginosa

View Answer

Answer: b [Reason:] In bacillary dysentery, Shigella bacteria penetrate into and kill the epithelial cells of the colon, then spread to adjacent cells, which are in turn killed.

5. Wounds and burns represent one active mechanism.
a) True
b) False

View Answer

Answer: b [Reason:] Wounds and burns represent one passive mechanism and they can introduce pathogens directly into the underlying tissues.

6. Bacillary dysentery is caused by which of the following microorganism?
a) Clostridium perfringens
b) Borrelia sp.
c) Shigella
d) Pseudomonas aeruginosa

View Answer

Answer: c [Reason:] Bacillary dysentery is caused by Shigella bacteria which penetrate into and kill the epithelial cells of the colon, then spread to adjacent cells, which are in turn killed.

7. In which of the following body part does the influenza virus does not penetrate?
a) small intestine
b) nasopharynx
c) trachea
d) bronchi

View Answer

Answer: a [Reason:] The influenza virus penetrates the epithelial cells lining the nasopharynx, trachea and bronchi.

8. Which of the following is an arthropod?
a) Clostridium perfringens
b) Borrelia sp.
c) Shigella
d) Pseudomonas aeruginosa

View Answer

Answer: b [Reason:] Arthropods follow passive penetration such as that by Borrelia species which causes relapsing fever in humans.

Interview MCQ Set 5

1. Among the following which one is the most effective method of killing microorganisms?
a) High temperature
b) Low temperature
c) High temperature,high moisture
d) Low temperature,high moisture

View Answer

Answer: c [Reason:] High temperatures combined with high moisture are one of the most effective methods of killing microorganisms. It is important to distinguish between dry heat and moist heat in any procedure for microbial control.

2. How much time is required by spores of Clostridium botulinum to be killed by moist heat at 1200C?
a) 2 hours
b) 4 to 20 minutes
c) 24 hours
d) 6-7 hours

View Answer

Answer: b [Reason:] Spores of Clostridium botulinum are killed in 4 to 20 minutes by moist heat at 1200C, whereas a 2 hours exposure to dry heat at the same temperature is required.

3. Vegetative cells are much more sensitive to heat than are spores.
a) True
b) False

View Answer

Answer: a [Reason:] Vegetative cells are much more sensitive to heat than the spores because of the higher level of water activity in the vegetative cells.

4. Which of the following conditions are required for determination of thermal death time?
a) temperature is varied
b) time is fixed
c) temperature is fixed and time is varied
d) temperature is fixed and time is not selected

View Answer

Answer: c [Reason:] In thermal death time, the temperature is selected as the fixed point and the time is varied. It refers to the shortest period of time to kill a suspension of bacteria or spores at a prescribed temperature and under specific conditions.

5. Which of the following apparatus is used to provide steam under regulated pressure?
a) autoclave
b) laminar air flow
c) incubator
d) hot oven

View Answer

Answer: a [Reason:] The laboratory apparatus designed to use steam under regulated pressure is called an autoclave. It is essentially a double-jacketed steam chamber which can maintain steam under pressure and temperature.

6. The general pressure at which the autoclave is operated is ___________
a) 5 Psi
b) 20 Psi
c) 15 Psi
d) 40 Psi

View Answer

Answer: c [Reason:] Generally the autoclave is operated at a pressure of approximately 15 Psi at 121.50C.It is not the pressure that kills the organisms but the temperature of the steam.

7. Some amount of air is also essential inside the chamber of the autoclave.
a) True
b) False

View Answer

Answer: b [Reason:] In the operation of an autoclave it is absolutely essential that the air in the chamber be completely replaced by saturated steam. If air is present, it will reduce the temperature obtained within the chamber substantially below.

8. Which of the following methods is used for killing microorganisms of only certain types and not all microorganisms?
a) Pasteurization
b) Incineration
c) Boiling water
d) Fractional Sterilization

View Answer

Answer: a [Reason:] In pasteurization, milk, cream, and certain alcoholic beverages are subjected to a controlled heat treatment which kills microorganisms of certain types but does not destroy all organisms.

9. Which of the following instruments is used to perform tyndallization?
a) Autoclave
b) Steam Arnold
c) Gas oven
d) Incubator

View Answer

Answer: b [Reason:] For tyndallization or fractional sterilization the apparatus used is the Steam Arnold however an autoclave can also be used if a free-flowing steam is used.

10. Which of the following actions occur due to low temperature?
a) coagulation of proteins
b) death of microorganisms
c) rate of metabolism is reduced
d) denatures proteins

View Answer

Answer: c [Reason:] Temperatures below the optimum for growth depresses the rate of metabolism and if the temperature is sufficiently low, growth and metabolism ceases. Low temperature are also useful for preservation of cultures.

11. Which of the following are resistant to desiccation?
a) gonococci
b) streptococci
c) meningococci
d) bacillus

View Answer

Answer: b [Reason:] Streptococci are much more resistant to dessication, some survive weeks after being dried but species of Gram-negative cocci are very sensitive to dessication.

12. Passage of water from a low solute concentration into the cell is referred to as ______________
a) plasmoptysis
b) plasmolysis
c) isotonic
d) hypertonic

View Answer

Answer: a [Reason:] The passage of water from a low solute concentration into the cell is termed plasmoptysis. The pressure built up within the cell as a result of this water intake is termed osmotic pressure.

13. Which of the following radiations have the energy to knock electrons away from molecules and ionize them?
a) Non-ionizing radiations
b) Acoustic radiations
c) Subatomic particles
d) Ionizing radiations

View Answer

Answer: d [Reason:] Gamma rays and x-rays are called ionizing radiations because they have enough energy to knock electrons away from molecules and ionize them. When such radiations pass through cells, they create free hydrogen radicals, hydroxyl radicals and some peroxides which causes intracellular damage.

14. Wavelengths around ___________ have the highest bactericidal efficiency.
a) 150 Å
b) 3900 Å
c) 2650 Å
d)1500 Å

View Answer

Answer: c [Reason:] The ultraviolet portion of the spectrum includes all radiations from 150 to 3900 Å.Wavelengths around 2650 Å have the highest bactericidal efficiency.

15. Which of the following inhibits DNA replication?
a) cathode rays
b) UV light
c) x-rays
d) gamma rays

View Answer

Answer: b [Reason:] Ultraviolet light is absorbed by many cellular materials but most significantly by the nucleic acids where it does the most damage.Pyrimidine dimers are formed due to which DNA replication is inhibited and mutations can result.

16 .Which material is used for the Berkefeld filter?
a) diatomaceous earth
b) asbestos pad
c) porcelain
d) sintered glass disks

View Answer

Answer: a [Reason:] Filters can remove microorganisms from liquids or gases. The Berkefeld filter is made up of diatomaceous earth.