Category: MICROBIOLOGY Objective Questions

Microbiology Multiple Choice Questions on “Growth Cycle of Bacteria”.

1. The portion of the growth curve where rapid growth of bacteria is observed is known as ____________
A. Lag phase
B. Logarithmic phase
C. Stationary phase
D. Decline phase
Answer: B
Clarification: A typical growth curve has four regions. An initial period of no growth known as the lag phase, followed by rapid growth known as logarithmic phase. No growth is observed in the stationary phase and death phase.

2. The growth of bacterial population follows a geometric progression.
A. True
B. False
Answer: A
Clarification: The bacteria show growth by following binary fission as means of reproduction. Thus, if we start with a single bacterium, the increase in population is by geometric progression.

3. In the growth equation: n = 3.3 (log10 N – log10 No), n stands for ____________
A. total population
B. initial population
C. number of generations
D. growth constant
Answer: C
Clarification: In the above formula, n stands for the number of generations that have taken place after the growth.

4. Lag phase is also known as ___________
A. period of initial adjustment
B. transitional period
C. generation time
D. period of rapid growth
Answer: A
Clarification: In the lag phase, the bacteria maybe deficient in enzymes or coenzymes which must first be synthesized and thus time is required for adjustments in the physical environment. So it is also known as a period of initial adjustment.

5. The generation time for E.coli is ________
A. 20 minutes
B. 35 minutes
C. 2 minutes
D. 13 minutes
Answer: A
Clarification: The generation time for E.coli at a temperature of 37 degrees Celsius lies in the range of 15-20 minutes generally.

6. During exponential phase, growth rate is _______
A. same as generation time
B. reciprocal of generation time
C. time required for population to double
D. rate of doubling population
Answer: B
Clarification: During exponential growth, the growth rate (R) i.e., the number of generations per hour, is the reciprocal of the generation time g. Growth rate is the slope of the straight line obtained when the log number of cells is plotted against time.

7. In which of the following phase secondary metabolites are produced during growth?
A. Lag phase
B. Log/Exponential phase
C. Stationary phase
D. Death phase
Answer: C
Clarification: During the stationary phase, there is complete utilization of the nutrients present in media and thus produce secondary metabolites which are then used in different industries.

8. Which phase shows the reproduction rate equal to the equivalent death rate?
A. Log phase
B. Stationary phase
C. Death phase
D. Lag phase
Answer: B
Clarification: In the stationary phase there is a complete cessation of division and thus the reproduction rate is balanced by an equivalent death rate.

9. Which of the following is used to grow bacterial culture continuously?
A. Chemostat
B. Hemostat
C. Coulter-Counter
D. Turbidostat
Answer: A
Clarification: Chemostat is used for continuous cultivation. This system depends on the fact that the concentration of an essential nutrient within the culture vessel will control the growth rate of the cells.

10. The average size of the cells in the exponential phase is ___________
A. larger than the initial size
B. smaller than the initial size
C. equal to the initial size
D. maybe smaller or larger than the initial size
Answer: B
Clarification: During the exponential phase, the cells divide steadily at a constant rate and thus give a straight line. So the average size of cells goes on decreasing than the initial size due to binary fission.

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Microbiology Multiple Choice Questions on “World of Bacteria I – Facultatively Anaerobic Gram – Negative Rods”.

1. The cell diameter of bacteria belonging to family Enterobacteriaceae is ____________
A. 1 m
B. 1 cm
C. .3-1.5 micrometre
D. 5 micrometer
Answer: C
Clarification: A distinctive feature of the family Enterobacteriaceae is that the cell diameter is 0.3 to 1.5 micrometers.

2. What is the cell shape of the organisms belonging to the family Enterobacteriaceae?
A. vibrio
B. coccus
C. bacillus
D. straight rod
Answer: D
Clarification: The cell shape of organisms belonging to the family Enterobacteriaceae is that of a straight rod.

3. Enterobacteriaceae possesses endoflagella.
A. True
B. False
Answer: B
Clarification: Enterobacteriaceae possesses lateral flagella and moves by means of it. It does not possess endoflagella.

4. Which of the following genus of bacteria causes gastroenteritis in humans?
A. Salmonella
B. Enterobacter
C. Escherichia
D. Shigella
Answer: C
Clarification: Some bacteria of genus Escherichia causes gastroenteritis and some others can also cause urinary tract infections.

5. Enterobacter sp. gives negative result for Voges-Proskauer test.
A. True
B. False
Answer: B
Clarification: Enterobacter sp. gives positive results for Voges-Proskauer test by giving a reddish-pink colouration.

6. Which of the following genus of bacteria under the family Enterobacteriaceae is mainly associated with plants?
A. Erwinia
B. Serratia
C. Proteus
D. Yersinia
Answer: A
Clarification: Bacteria belonging to the genus Erwinia differ from most other Enterobacteriaceae by being mainly associated with plants. They are often plant pathogens, causing diseases such as blights, leaf spot, wilts, etc.

7. Which of the following is the causative agent of the plague?
A. Y.enterocolitica
B. Y.pestis
C. P.mirabilis
D. E.coli
Answer: B
Clarification: Yersiniae are parasites of animals but can also cause infections in humans. For example, Y.pestis is the causative agent of the plague.

8. The family Vibrionaceae is _________________
A. oxidase-positive
B. oxidase-negative
C. coccus shaped
D. non-motile
Answer: A
Clarification: A distinctive feature of the family Vibrionaceae is that they are usually oxidase-positive. They are motile by means of polar flagella and cell shape is that of curved or straight rods.

9. Which of the following genus shows the characteristic of bioluminescence?
A. Aeromonas
B. Zymomonas
C. Vibrio
D. Haemophilus
Answer: C
Clarification: Some species of genus Vibrio can emit light of a blue-green color(bioluminescence), an oxygen-dependent reaction catalyzed by the enzyme luciferase.

10. Among the given families, which family contains organisms that are non-motile?
A. Enterobacteriaceae
B. Vibrionaceae
C. Pseudomonadaceae
D. Pasteurellaceae
Answer: D
Clarification: Pasteurellaceae contains cells that are nonmotile. Their cell diameter is very small and the shape is that of a straight rod.

11. The X factor and/or the V factor is required by which genus of bacteria?
A. Pasteurella
B. Haemophilus
C. Actinobacillus
D. Zymomonas
Answer: B
Clarification: Haemophilus bacteria is distinguished by unusual nutritional requirements: the X factor (heme, occurring in blooD. and/or the V factor(the coenzyme nicotinamide adenine dinucleotide).

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Microbiology Multiple Choice Questions on “Morphology of Protozoa”.

1. Leishmania donovani measures _____________ in length.
A. 600 micrometre
B. 1 to 4 micrometre
C. 2 mm
D. 2000 micrometre
Answer: B
Clarification: Leishmania donovani, the cause of human disease kala azar, measures 1 to 4 micrometre in length.

2. Protozoan mobility is due to the fibrils present.
A. True
B. False
Answer: B
Clarification: Protozoan contractility is probably due to the fibrils. Submicroscopic protein fibrils are groups of parallel fibrils in the cytoplasm.

3. Plasmagel is known as __________________
A. cytoplasm
B. endoplasm
C. ectoplasm
D. myonemes
Answer: C
Clarification: Plasmagel is known as the ectoplasm. The cytoplasm is differentiated into endoplasm and ectoplasm. The ectoplasm is more gel-like and the endoplasm is more voluminous and fluid.

4. Golgi bodies are also known as __________________
A. dictyosomes
B. kinetosomes
C. blepharoplasts
D. myonemes
Answer: A
Clarification: Golgi complexes are also known as dictyosomes which means piles of membranous sacs.

5. The micronucleus in protozoa is concerned with reproductive activity.
A. True
B. False
Answer: A
Clarification: The micronucleus is concerned with reproductive ability whereas the macronucleus controls the metabolic activities and regeneration processes.

6. How many haploid chromosomes are present in Spirotrichonympha polygyra?
A. 60
B. 7
C. 2
D. 40
Answer: C
Clarification: It has been shown that number of chromosomes is constant for a particular species of protozoan. Spirotrichonympha polygyra has 2 haploid chromosomes.

7. Amoeba proteus have a diffuse layer of which of the following over the plasmalemma?
A. glucose
B. chitin
C. cellulose
D. mucopolysaccharides
Answer: D
Clarification: Amoeba proteus have a diffuse layer of mucopolysaccharides over the plasmalemma. This layer is thought to play an important role in pinocytosis or in adhesion of the cell to the substratum.

8. Among the following which layer is directly apposed to the cell surface?
A. tests
B. theca
C. shells
D. loricae
Answer: B
Clarification: The theca is a secreted layer directly apposed to the cell surface. Tests, shells, and lorica are coverings that are loosely apposed to the cell surface. Tests, shells, and lorica are coverings that are loose-fitting.

9. Which of the following is the actual opening in ciliates through which food is ingested?
A. cytosome
B. oral groove
C. peristome
D. cytopharynx
Answer: A
Clarification: In ciliates the cytosome is the actual opening through which food is ingested. It ranges from a simple round opening to a slitlike structure surrounded by feeding membranelles.

10. Which of the following protective structures occur in the tentacles of suctorian protozoa?
A. mucocysts
B. trichocysts
C. toxicysts
D. haptocysts
Answer: D
Clarification: Haptocysts occur in the tentacles of suctorian protozoa and are used to contact and immobilize prey.

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Microbiology Multiple Choice Questions on “Industrial Uses of Yeasts”.

1. Which among the following are not used as raw materials for alcohol production?
A. corn
B. molasses
C. whey
D. grapes
Answer: C
Clarification: Corn, molasses, sugar beets, potatoes, and grapes are some of the common raw materials employed throughout the world for alcohol fermentation.

2. The organism used for alcohol fermentation should have a high tolerance for alcohol.
A. True
B. False
Answer: A
Clarification: It is imperative that the culture be one that grows vigorously and has a high tolerance for alcohol as well as a capacity for producing a large yield of alcohol.

3. What is the pH required for the production of baker’s yeast?
A. 1 to 2
B. 4 to 5
C. 7 to 8
D. 10 to 12
Answer: B
Clarification: In the manufacture of baker’s yeast, the medium is adjusted to an acid pH of 4 to 5, which helps retard bacterial growth.

4. The leavening or rising of dough is due to which of the following gases?
A. oxygen
B. carbon dioxide
C. hydrogen
D. sulphur dioxide
Answer: B
Clarification: The carbon dioxide produced during the fermentation by baker’s yeast is responsible for the leavening or rising of the dough.

5. Which of the following instrument is used for the recovery of yeast cells?
A. fermenter
B. centrifuge
C. filter press
D. mash storage
Answer: C
Clarification: The cells are finally recovered on a filter press, small amounts of vegetable oil are added as a plasticizer, and then this mass of cells is molded into blocks.

6. Which of the following product is used as a food condiment?
A. Baker’s yeast
B. Ethanol
C. Wine
D. Soy sauce
Answer: D
Clarification: Soy Sauce is produced by the yeast Saccharomyces rouxii and is used as a food condiment.

7. Which of the following yeast can be used to produce microbial protein?
A. Saccharomyces cerevisiae
B. Candida milleri
C. Eremothecium ashbyi
D. Candida utilis
Answer: D
Clarification: Candida utilis is yeast used for producing microbial protein which is used as an animal food supplement (single-cell protein) from paper-pulp waste.

8. The medium for production of Baker’s yeast contains only molasses and inoculum.
A. True
B. False
Answer: B
Clarification: In the manufacture of baker’s yeast the “stock” strain is inoculated into a medium that frequently contains molasses and corn-steep liquor.

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Microbiology Multiple Choice Questions on “Viruses Containing Single – Stranded RNA”.

1. Polioviruses belong to which of the following groups?
A. enteroviruses
B. rhinoviruses
C. foot and mouth disease viruses
D. retroviruses
Answer: A
Clarification: Polioviruses belong to the enteroviruses because they are found in the intestines and excreted in the feces. They cause mainly intestinal infections and sometimes infections of the respiratory tract; neurological disease may also be produced.

2. Where does polioviruses multiply first?
A. skin
B. oropharynx
C. lymph nodes
D. spinal cord
Answer: B
Clarification: Polioviruses multiply in the oropharynx or intestinal mucosa, pass to the lymphatic system and eventually reach the bloodstream.

3. The Sabin vaccine is 70 to 90 percent effective for immunization against poliomyelitis.
A. True
B. False
Answer: B
Clarification: The Salk virus is 70 to 90 percent effective and is administered in a series of three intramuscular injections.

4. At what pH values are the rhinoviruses destroyed?
A. 7
B. 12-13
C. 1-4
D. 5-7
Answer: C
Clarification: Rhinoviruses differ from enteroviruses by being destroyed at pH values of less than 5 (such as would occur in the stomach) and by having an optimal growth temperature at 33 degrees C.

5. Complement- fixation is done for laboratory diagnosis of which of the following disease?
A. Poliomyelitis
B. Mumps
C. Measles
D. FMD
Answer: D
Clarification: Laboratory diagnosis of FMD is done by complement-fixation, virus-neutralization, or mouse-inoculation tests.

6. Eastern equine encephalitis is more fatal than western equine encephalitis.
A. True
B. False
Answer: A
Clarification: Eastern equine encephalitis has a high mortality rate (50 to 70 percent), whereas western equine encephalitis virus infections are seldom fatal (3%).

7. Yellow fever is caused by ____________
A. Alphaviruses
B. Rubellaviruses
C. Flaviviruses
D. Pestiviruses
Answer: C
Clarification: Yellow fever is caused by flaviviruses that differ from others in causing a disease in which the liver, kidney, and other organs are affected.

8. Which of the following viruses consists of a helical nucleocapsid?
A. Picornaviruses
B. Togaviruses
C. Adenoviruses
D. Coronaviruses
Answer: D
Clarification: Coronaviruses have a helical nucleocapsid and contain single-stranded RNA of the (+) type.

9. Which drug is used to cure influenza caused by type A strains?
A. Penicillin
B. Amantadine
C. Ampicillin
D. Tetracycline
Answer: B
Clarification: A synthetic drug, amantadine, can prevent and even help to cure influenza caused by type A strains; it acts by preventing the penetration and uncoating of the virus after it attaches to a host cell.

10. Which of the following is incorrect with respect to Paramyxoviruses?
A. large (125 to 250 nm)
B. core of single-stranded (—) RNA
C. rna is segmented
D. hemagglutinin and neuraminidase activities occur together
Answer: C
Clarification: The paramyxoviruses are larger (125 to 250 nm), the RNA is segmented and only the (—) strand is present, and the hemagglutinin and neuraminidase activities occur together in a single kind of surface glycoprotein (HN).

11. Crimean-Congo hemorrhagic fever is transmitted by _____________
A. mosquitoes
B. ticks
C. biting flies
D. rabbits
Answer: B
Clarification: Crimean-Congo hemorrhagic fever occurs in Africa and Asia and is spread by ticks. This disease is caused by Bunyaviruses.

12. What is the shape of the Rhabdoviruses?
A. bullet
B. circular
C. brick shaped
D. ovoid
Answer: A
Clarification: Rhabdoviruses are 70 to 80 by 130 to 240 nm in size and have a characteristic bullet shape. They have a helical nucleocapsid and contain single-stranded RNA of the (—) type.

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