Category: MICROBIOLOGY Objective Questions

Microbiology Multiple Choice Questions on “Bacteria Cultivation – Physical Conditions Required for Growth”.

1. The temperature that allows for most rapid growth during a short period of time is known as __________
A. Minimum Temperature
B. Maximum Temperature
C. Optimum Temperature
D. Growth Temperature
Answer: C
Clarification: The temperature that allows for the most rapid growth during a short period of time(12 to 24 hrs) is known as the optimum temperature. Maximum temperature for growth lies very close to the optimum temperature whereas minimum temperature for growth is usually much lower than the optimum.

2. Mesophiles are group of bacteria that grow within the temperature range of?
A. 0-20 degree Celsius
B. 25-40 degree Celsius
C. 45-60 degree Celsius
D. more than 60 degree Celsius
Answer: B
Clarification: Mesophiles grow best within a temperature range of 25 to 40 degree Celsius. All bacteria that are pathogenic for humans and warm-blooded animals are mesophiles, most growing best at about body temperature(37 degree Celsius).

3. Which of the following factors are responsible for the stability of thermophiles at high temperatures?
A. increased leakage of cell components
B. presence of large no. of polar amino acids and alpha-helix protein
C. thermal stability of ribosomes
D. presence of Inositol diphosphate and thermal stability of ribosomes
Answer: D
Clarification: Factors that have been implicated in the ability to grow at high temperature is increased thermal stability of ribosomes. The cytoplasmic membrane of thermophiles also contains Inositol diphosphate or Inositol triphosphate which can tolerate high temperature and maintains the fluidity of the membrane.

4. The bacterium Staphylococcus aureus is which type of bacteria?
A. Psychrophile
B. Mesophile
C. Thermophile
D. Mesophile and psychrophile
Answer: B
Clarification: Staphylococcus aureus is a mesophilic bacteria which can grow in the temperature range of 6.5-46 degree Celsius and has an optimum temperature at 30-37 degree Celsius.

5. Microaerophilic bacteria require low levels of oxygen for growth.
A. True
B. False
Answer: A
Clarification: Microaerophilic bacteria require low levels of oxygen for growth but it cannot tolerate the level of oxygen present in an air atmosphere.

6. The Reactive Oxygen Species(ROS) produced by some bacteria are degraded by which of the following enzymes?
A. Peroxidase
B. Lyase
C. Catalase
D. Superoxide dismutase, Catalase and Peroxidase
Answer: D
Clarification: In some cases, oxygen may accept large number of free electrons and produces Reactive Oxygen Species (ROS). They are harmful as they degrade macromolecules required for growth and nutrition. But aerobic bacteria contains three different enzymes-Superoxide dismutase, Catalase and Peroxidase which eliminates the different ROS.

7. Which of the following ROS is a powerful oxidizing agent?
A. Superoxide radical
B. Hydrogen peroxide
C. Hydroxyl radical
D. Singlet oxygen
Answer: B
Clarification: Superoxide radicals form toxic substances such as hydrogen peroxide. Hydrogen peroxide is not a free radical, but it is a powerful oxidizing agent.

8. The GasPak system is suitable for which of the following?
A. Aerobic bacteria
B. Anaerobic bacteria
C. Facultatively anaerobic bacteria
D. Microaerophilic bacteria
Answer: B
Clarification: GasPak Jar is a system for anaerobic bacteria. In this jar media is inoculated and placed in the jar. To this water is added, causing the evolution of Hydrogen gas and Carbon dioxide. Hydrogen gas reacts with oxygen on the surface of the palladium catalyst, forming water and establishing anaerobic conditions.

9. Which of the following are functions of phosphates used in the preparation of media?
A. they act as buffer
B. source of phosphorous
C. act as “reserve alkali”
D. they act as buffer and is a source of phosphorous
Answer: D
Clarification: The phosphates are used widely in the preparation of media because they are the only inorganic agents that buffer in the physiologically important range around neutrality and that are relatively non-toxic to microorganisms. In addition, they provide a source of phosphorous, which is an essential element of growth.

10. The optimum pH for the growth of most bacteria lies between _______
A. 5-9
B. 6.5-7.5
C. 2-3.5
D. 9-9.5
Answer: B
Clarification: pH is an important physical condition controlling the growth of bacteria. For most bacteria, the optimum pH for growth lies between 6.5 and 7.5. This pH of the media is maintained by using a buffer into the medium.

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Microbiology Multiple Choice Questions on “World of Bacteria I – Spirochetes”.

1. The endoflagella is present in which class of bacteria?
A. Spirilla
B. Spirochetes
C. Bacillus
D. Coccus
Answer: B
Clarification: Spirochetes have an ability to twist or contort their shape due to the occurrence of a special kind of flagella termed periplasmic flagella or endoflagella.

2. Where is the endoflagella located in Spirochetes?
A. In the cell membrane
B. In the cytoplasm
C. In the peptidoglycan layer
D. In the periplasmic space
Answer: D
Clarification: In spirochetes, the endoflagella or as it is called periplasmic flagella is located between the outer membrane and the protoplasmic cylinder; thus they are located in the periplasmic space of the cell.

3. Spirochetes like other bacteria swim best in media of low viscosity.
A. True
B. False
Answer: B
Clarification: Spirochetes because of the added advantage of having an endoflagella swims best in media of high viscosity, whereas bacteria with ordinary flagella swim best in media of low viscosity.

4. Which of the following methods is used for viewing spirochetes?
A. Bright-field microscopy
B. Phase-contrast microscopy
C. Dark-field microscopy
D. Electron microscopy
Answer: C
Clarification: Most spirochetes are so thin that they cannot be easily seen by light microscopy, even when Gram-stained; however, dark-field microscopy does provide sufficient contrast and is the method of choice for visualizing these organisms.

5. The family Leptospiraceae are aerobes.
A. True
B. False
Answer: A
Clarification: The family Leptospiraceae of spirochetes are aerobes who use long-chain fatty acids as the carbon and energy source.

6. Which among the following are microaerophilic bacteria?
A. Spirochaeta
B. Cristispira
C. Treponema
D. Borrelia
Answer: D
Clarification: Borrelia is the genus of bacteria belonging to the class Spirochaetaceae and are microaerophilic.

7. Which of the following bacteria causes syphilis in humans?
A. Treponema dysenteriae
B. Treponema pallidum
C. Leptospira biflexa
D. Leptospira interrogans
Answer: B
Clarification: Treponema pallidum causes syphilis in humans and is microaerophilic. They belong to the family Spirochaetaceae and are found in the mouth, intestinal tract, and genital areas of humans and animals.

8. Which of the following have bipolar tufts of flagella?
A. Aquaspirillum
B. Azospirillum
C. Cristispira
D. Borrelia
Answer: A
Clarification: Aquaspirilla are helical or vibroid organisms that typically possess bipolar tufts of flagella. They may be aerobic or microaerophilic and occur in a stagnant stream or pond water.

9. Which of the following causes diarrhea in humans?
A. A.lipoferum
B. L.interrogans
C. C.jejuni
D. E.coli
Answer: C
Clarification: C.jejuni causes diarrhea in humans and belong to the genus Campylobacters. They are microaerophilic parasites and occur in the reproductive organs, intestinal tract, and oral cavity of humans and other mammals.

10. Which genus among the following has certain similarities to the genus Bdellovibrio?
A. Azospirillum
B. Oceanospirillum
C. Campylobacter
D. Vamprirovibrio
Answer: D
Clarification: The genus Vampirovibrio has certain similarities to the genus Bdellovibrio, but the organisms attack eukaryotic algae, not bacteria.

11. Which group of bacteria among the following give a positive reaction by the oxidase test?
A. Spirochetes
B. Aerobic/Microaerophilic, Motile, Helical/Vibroid, Gram-negative bacteria
C. Non-motile, Gram-negative, Curved bacteria
D. Aerobic, Gram-negative rods and cocci
Answer: B
Clarification: Aerobic/Microaerophilic, motile, Helical/Vibroid, Gram-negative bacteria are organisms that usually give a positive reaction by the oxidase test. It is a laboratory test based on the presence of cytochrome c.

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Microbiology Multiple Choice Questions on “Algae – Classification”.

1. Carpogonia is the female sex organ in which of the algae?
A. Rhodophycophyta
B. Xanthophycophyta
C. Chrysophycophyta
D. Chlorophycophyta
Answer: A
Clarification: Rhodophycophyta reproduces sexually heterogamously by the union of well-differentiated nonmotile male and female germ cells, the spermatia and carpogonia (female sex organs), respectively.

2.The xanthophyte walls are typically of _____________________
A. chitin
B. cellulose
C. cellulose and pectin
D. starch
Answer: C
Clarification: The xanthophye walls are typically of cellulose and pectin. The cellular storage product is an oil or (a branched glucan) chrysolaminarin.

3. Vaucheria is a single-celled organism.
A. True
B. False
Answer: B
Clarification: Vaucheria has a very large macroscopic filamentous form. It is widely distributed on moist soil and water.

4. Chrysamoeba exists in which of the following forms?
A. nonmotile coccoid
B. filamentous
C. amoeboid
D. motile amoeboid
Answer: D
Clarification: Chrysamoeba is a strongly amoeboid genus with flagella. It belongs to the group of golden algae.

5. Kelps are which of the following type of algae?
A. red algae
B. yellow algae
C. brown algae
D. green algae
Answer: C
Clarification: Brown algae are structurally quite complex and kelps belong to this group. Kelps are large, the individual plants reaching a length of several hundred feet.

6. Frustules are found in which of the following algae?
A. Bacillariophycophyta
B. Chlorophycophyta
C. Euglenophycophyta
D. Rhodophycophyta
Answer: A
Clarification: Bacillariophycophyta or diatoms produce shells (cell walls) containing silica, some of which are very beautiful. Shells of diatoms are called frustules.

7. Euglena contains cell wall made up of cellulose.
A. True
B. False
Answer: B
Clarification: Euglena has no cell wall containing cellulose. The outer membrane is an organized periplast.

8. Which of the following are formed in pyrenoids?
A. oil
B. glucose
C. starch
D. silica
Answer: C
Clarification: The chloroplasts of green algae often contain dense regions called pyrenoids, on which surface starch granules are formed.

9.In Chlamydomonas the most common method of sexual reproduction is ________________
A. isogamy
B. heterogamy
C. oogamy
D. spore formation
Answer: A
Clarification: Sexua reproduction occurs in many species of Chlamydomonas, by isogamy, heterogamy, or oogamy in which isogamy is by far the most common. The zygote divides to form four or eight motile haploid cells are released.

10. Which of the following is a colonial green alga?
A. Chlamydomonas
B. Chlorella
C. Volvox
D. Spirogyra
Answer: C
Clarification: Volvox is a colonial green alga which may form water blooms. Its colonies are visible to the naked eye.

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Microbiology Multiple Choice Questions on “Microorganisms and Industry”.

1. Which of the following is not a desired characteristic of the organism to be used for industrial application?
A. should produce less amount of product
B. should be readily available
C. should grow rapidly
D. should be nonpathogenic
Answer: A
Clarification: The organism to be used must be able to produce appreciable amount of the product. It should be readily available and should grow rapidly and vigorously. It should be nonpathogenic.

2. Industrial fermentation are performed in large tanks of capacity ______________
A. 100 gal
B. 1000 gal
C. 50,000 gal
D. 10,000 gal
Answer: C
Clarification: Industrial fermentation are performed in large tanks; capacities of 50,000 gal are not unusual.

3. Solvents and enzymes are found in which of the following categories of microbial products?
A. Pharmaceutical chemicals
B. Commercially valuable chemicals
C. Food supplements
D. Alcoholic beverages
Answer: B
Clarification: Solvents, enzymes, and intermediate compounds for the synthesis of other substances are representative of the kinds of substances produced commercially by microorganisms.

4. Which of the following enzymes cut the DNA molecule at a particular nucleotide sequence?
A. restriction endonuclease
B. exonuclease
C. ligase
D. polymerase
Answer: A
Clarification: Restriction endonuclease cut double-stranded DNA molecules at particular nucleotide sequences and thus produce a well-defined DNA fragment for a given enzyme and a given DNA.

5. Eco R1 cuts the plasmid DNA and the donor DNA such that both the ends are same.
A. True
B. False
Answer: B
Clarification: The endonuclease Eco R1 cuts the plasmid DNA and the donor DNA in a manner such that the ends of each are identical and self-complementary.

6. Which of the following product is used for the treatment of blood clots?
A. insulin
B. interferon
C. urokinase
D. somatostatin
Answer: C
Clarification: The pharmaceutical industry has already produced several products for human therapy by the help of genetic engineering such as urokinase that is used for the treatment of blood clots; human insulin and interferons.

7. VP3 protein is isolated from which of the following viruses?
A. TMV
B. HIV
C. HRV
D. FMDV
Answer: D
Clarification: VP3 is the protein from the shell of the foot-and-mouth disease virus (FMDV), which can act as a vaccine for immunizing livestock against foot-and-mouth disease.

8. Transfection involves the introduction of plasmid hybrid DNA into the host cell.
A. True
B. False
Answer: B
Clarification: Transfection involves the introduction of phage hybrid DNA into the host cell whereas transformation involves the introduction of plasmid hybrid DNA into a competent host bacterial cell.

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Microbiology Questions and Answers for Entrance exams focuses on “Diseases Caused by Staphylococcus, Streptococcus and Bacillus”.

1. Which of the following toxins cause damage to the tissue cells by its phospholipase action?
A. alpha toxin
B. delta toxin
C. protein A
D. coagulase
Answer: B
Clarification: Delta toxin damages tissue cells by its action as a phospholipase. It is produced by human strains of S. aureus.

2. Which of the following microorganism causes lesions in the form of abscesses?
A. Staphylococcus aureus
B. Streptococcus pyogenes
C. Streptococcus pneumoniae
D. Clostridium perfringens
Answer: A
Clarification: Staphylococcus aureus causes localized infections in which the characteristic lesion is a walled-off fort called the abscess— a cavity filled with pus cells (neutrophils), dead tissue, and bacteria.

3. Antibiotics can easily reach the staphylococci.
A. True
B. False
Answer: B
Clarification: Antibiotics have difficulty in reaching the staphylococci and may have to be administered to a patient for a long period in order to be effective.

4. Streptococus pyogenes comprises which Lancefield group?
A. A
B. B
C. C
D. D
Answer: A
Clarification: Streptococus pyogenes comprises Lancefield group A. This organism causes several diseases like sore throat, scarlet fever etc.

5. Which of the following microbe does not belong to Group D enterococci group?
A. S. faecalis
B. S. faecium
C. S. durans
D. S. bovis
Answer: D
Clarification: S. bovis belongs to Group D nonenterococci group. All other above microbes belong to Group D enterococci group.

6. Scarlet fever is similar to the pharyngitis in all respects.
A. True
B. False
Answer: B
Clarification: Scarlet fever is similar to the pharyngitis except for the skin rash that appears because of the erythrogenic toxin.

7. Which of the following immunity is protective against infection by S.pyogenes?
A. cell-mediated immunity
B. antigen-antibody immunity
C. humoral immunity
D. no cure present
Answer: C
Clarification: The only type of immunity that is protective against infection by S. pyogenes is humoral immunity: antibodies against M proteins act as opsonins, enhancing phagocytosis of the streptococci.

8. Puerperal fever is a streptococcal infection of the ______________
A. kidney
B. skin
C. uterus
D. heart
Answer: C
Clarification: Puerperal fever, sometimes called puerperal sepsis, is a streptococcal infection of the uterus of a mother and is acquired at childbirth.

9. Which of the following is a major virulence factor of Streptococcus pneumoniae?
A. polysaccharide capsule
B. M protein
C. streptolysin O
D. streptolysin S
Answer: A
Clarification: The major virulence factor is the polysaccharide capsule, which effectively inhibits phagocytosis.

10. Which drug is used for the treatment of anthrax?
A. erythromycin
B. penicillin
C. tetracycline
D. ampicillin
Answer: B
Clarification: Penicillin is the drug of choice for the treatment of anthrax. A live attenuated vaccine is available for prevention of anthrax in cattle and sheep.

To practice all areas of Microbiology for Entrance exams, .