Category: MICROBIOLOGY Objective Questions

Microbiology Multiple Choice Questions on “Bacteria Cultivation – Bacteriological Media”.

1. Which of the following is a characteristic of beef extract?
A. product resulting from the digestion of proteinaceous materials
B. aqueous extract of lean beef tissue
C. aqueous extract of yeast cells
D. complex carbohydrate obtained from certain marine algae
Answer: B
Clarification: Beef extract, a complex raw material used as ingredient for preparing bacteriological media is an aqueous extract of lean beef tissue concentrated to a paste.

2. Which of the following is used as a solidifying agent for media?
A. Beef extract
B. Peptone
C. Agar
D. Yeast extract
Answer: C
Clarification: Agar is used as a solidification agent for media and is not considered a source of nutrient to the bacteria. Agar dissolved in aqueous solutions, gels when the temperature is reduced below 45 degrees Celsius.

3. Which of the following is a rich source of B vitamins?
A. Peptone
B. Yeast extract
C. Beef extract
D. Agar
Answer: B
Clarification: Yeast extract which is an aqueous extract of yeast cells is a very rich source of the B vitamins and it also contains apart from it organic nitrogen and carbon compounds.

4. The isolation of gonorrhea-causing organism, Neisseria gonorrhoeae by the use of certain antibiotics in media is an example of which of the following?
A. Selective media
B. Differential media
C. Enriched media
D. Assay media
Answer: A
Clarification: The isolation of gonorrhea-causing organism, Neisseria gonorrhoeae, from a clinical specimen is facilitated by the use of media containing certain antibiotics; these antibiotics do not affect N.gonorrhoeae but do inhibit the growth of contaminating bacteria. This is an example of selective media as it allows the growth of only a particular microorganism.

5. Nutrient broth, a liquid media contains beef extract and peptone respectively in how much amounts?
A. 0.2%, 0.4%
B. 0.1%, 0.6%
C. 0.3%, 0.5%
D. 0.7%, 0.3%
Answer: C
Clarification: Nutrient broth which is the most widely used media in general bacteriological work, contains 0.3 percent beef extract and 0.5 percent peptone. It may also contain if required 0.8 percent NaCl to maintain the salt concentration.

6. Which of the following instrument is used for sterilizing the media after it has been prepared?
A. Autoclave
B. Laminar Air Flow Chamber
C. Inoculum Needle
D. Incubator
Answer: A
Clarification: Autoclave is a type of pressure cooker which has steam at 121.5 degree Celsius and under 15 psi pressure. This steam kills all the microbes present in the media and sterilizes it.

7. Colony formation can be observed in liquid media broth.
a)True
B. False
Answer: B
Clarification: If microbial growth is found in liquid media, then the media shows turbidity but no colony formation can be observed. But in solid media microbial growth can be observed by colony formation as the media is already turbid due to the presence of agar powder.

8. Which of the following is a Complex media for fungal growth?
A. Nutrient broth
B. Luria-Bertani media
C. Potato Dextrose Agar(PDA. media
D. Mac Conkey Agar media
Answer: C
Clarification: Complex media is a chemically undefined media where the exact composition is not known. For fungal growth, complex media used is Potato Dextrose Agar(PDA. media.

9. Which of the following are functions of Maintenance Media?
A. used for assay of vitamins, amino acids
B. used for determining the bacterial content
C. used for determining the type of growth produced by bacteria
D. used for the maintenance of the viability and physiological characteristics
Answer: D
Clarification: Satisfactory maintenance of the viability and physiological characteristics of culture over time may require a medium different from that which is optimum for growth. Prolific, rapid growth may also be associated with rapid death of the cells at the end of the growth phase. Thus, a maintenance medium is required then.

10. Which of the following bacteria requires nicotinic acid as a growth factor in their media?
A. Proteus vulgaris
B. Nitrosomonas sp.
C. E. coli
D. Leuconostoc mesenteroides
Answer: A
Clarification: Proteus vulgaris require nicotinic acid as a growth factor in their media along with glucose as a carbon source and also Ammonium Chloride.

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Microbiology Multiple Choice Questions on “Microbial Metabolism – Process of Protein Synthesis”.

1. The amino acids for protein synthesis is activated by the enzyme ______________
A. rna synthetase
B. aminoacyl-tRNA synthetase
C. tRNA synthetase
D. aminoacyl-mRNA synthetase
Answer: B
Clarification: The first step in protein synthesis is the activation of amino acids. The amino acids are activated by amino-acid activating enzymes called aminoacyl-tRNA synthetase.

2. The activation of amino acids requires energy.
A. True
B. False
Answer: A
Clarification: The activation of amino acids for protein synthesis requires energy in the form of ATP. There is a specific activating enzyme for each kind of amino acid.

3. tRNA has a _______________ structure.
A. strand-like
B. ball-like
C. clover-leaf
D. leaf-like
Answer: C
Clarification: tRNA has a clover-leaf structure.The tRNA functions in protein synthesis to carry amino acids to, and recognize codons in, mRNA.

4. Transfer RNA is a single chain of ___________ nucleotides.
A. 340
B. about 100
C. about 80
D. 200
Answer: C
Clarification: Transfer RNA is a single chain of about 80 nucleotides that is folded back upon itself and held in a clover-leaf arrangement by means of hydrogen bonding due to complementary base pairing.

5. The terminal sequence of nucleotides in all tRNA is __________
A. ACC
B. UGC
C. UCC
D. AGC
Answer: A
Clarification: The terminal sequence of nucleotides is adenylic-cytidylic-cytidilic (ACC. and is found in all tRNA. The amino acid to be carried is linked to the terminal nucleotide containing adenine.

6.The tRNA carries amino acids to the ____________
A. rRNA
B. mRNA
C. sRNA
D. hnRNA
Answer: B
Clarification: The tRNA carries amino acid to the mRNA attached to the surface of the ribosome. Here the amino acid is added to a growing polypeptide chain.

7. The ribosome of E.coli is made up of which two subunits?
A. 60S and 40S
B. 60S and 30S
C. 50S and 40S
D. 50S and 30S
Answer: D
Clarification: The ribosomes of E.coli have been studied extensively and have been found to consist of two subunits. The larger subunit is a 50S particle, while the smaller unit is a 30S particle.

8. S,the Svedberg unit is a measure of ____________________________
A. the size of the ribosome
B. the composition of the ribosome
C. how fast a particle sediments during ultracentrifugation.
D. how the subunits combine in a ribosome
Answer: C
Clarification: S is the Svedberg unit, a measure of how fast particle sediments during ultracentrifugation. The association of a 30S and 50S subunit to form a 70S ribosome shows that the sedimentation behavior of the 70S ribosome is not a simple addition of the units of the smaller particles.

9. Which of the following statement is correct?
A. The ribosome binds to any end of a mRNA
B. CTP is required for activation of amino acids
C. Activated amino acids bind to the 5’ end of a respective tRNA molecule
D. The protein chain dissociates from the last tRNA molecule
Answer: D
Clarification: The amino group of the amino acid on the second tRNA reacts with the active terminal carboxyl group on the amino acid of the first tRNA to form a dipeptide; the first tRNA is then released. The process is continued till the peptide chain is complete. Termination takes place at one of the nonsense codons and the chain dissociates from the last tRNA molecule.

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Microbiology Multiple Choice Questions on “Algae – Characteristics”.

1. Chlorophyll d is present in the members of _____________________
A. Xanthophycophyta
B. Phaeophycophyta
C. Rhodophycophyta
D. Chrysophycophyta
Answer: C
Clarification: Chlorophyll d is present only in the members of Rhodophycophyta. There are five chlorophylls a, b, c, d, e which are found in different organisms.

2. Fucoxanthin pigment is present in _______________
A. Rhodophycophyta
B. Xanthophycophyta
C. Phaeophycophyta
D. Chlorophycophyta
Answer: C
Clarification: Fucoxanthin is present in Phaeophycophyta and gives it its characteristic colour brown. Other pigments like carotene and chlorophyll a and c are also present along with fucoxanthin.

3. Phycoerythrin pigment is present in which algal division?
A. Xanthophycophyta
B. Rhodophycophyta
C. Chrysophycophyta
D. Phaeophycophyta
Answer: B
Clarification: Phycoerythrin and phycocyanin are biloproteins present in Rhodophycophyta. They are also present in cryptomonads.

4. Chrysolaminarin is the reserved food of ___________________
A. Chlorophycophyta
B. Phaeophycophyta
C. Xanthophycophyta
D. Bacillariophycophyta
Answer: C
Clarification: Chrysolaminarin is the reserved food of Xanthophycophyta which is the yellow-green algae along with oils.

5. Cell walls of diatoms are impregnated with _____________
A. chitin
B. cellulose
C. starch
D. silica
Answer: D
Clarification: Cell walls of diatoms are impregnated with silica, making them thick and very rigid; they are often delicately sculptured with intricate designs characteristic of the species or variety.

6. Chloroplasts of algae embedded in the midst of the cytoplasm is known as ________________
A. parietal
B. asteroidal
C. central
D. peripheral
Answer: B
Clarification: The chloroplasts may be massive structures situated near the wall which are known as parietal or embedded in the midst of the cytoplasm which are known as asteroidal.

7. Carotenes are oxygenated derivatives of hydrocarbons.
A. True
B. False
Answer: B
Clarification: Carotenes are linear, unsaturated hydrocarbons, and xanthophylls are oxygenated derivatives of these.

8. Two lateral flagella are present in which of the following groups of algae?
A. Rhodophycophyta
B. Xanthophycophyta
C. Phaeophycophyta
D. Bacillariophycophyta
Answer: C
Clarification: Phaeophycophyta or the brown algae consists of two lateral flagella. Dinoflagellate or cryptomonads also consists of two lateral flagella.

9. Gullet is present in which algae?
A. Euglenoids
B. Golden algae
C. Dinoflagellates
D. Green algae
Answer: A
Clarification: Euglenoids or Euglenophycophyta contain gullet which is anteriorly present. It contains 1, 2 or 3 equal or slightly apical flagella.

10. Which of the following are water-soluble pigments?
A. chlorophyll
B. biloproteins
C. carotenoids
D. fucoxanthin
Answer: B
Clarification: Biloproteins or phycobilins are water-soluble pigments whereas chlorophylls and carotenoids are lipid-soluble.

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Microbiology Multiple Choice Questions on “Microorganisms as Food”.

1. Which of the following microbe is used in the production of blue cheese?
A. Streptococcus thermophilus
B. Lactobacillus bulgaricus
C. Penicillium roqueforti
D. Rhizopus stolonifer
Answer: C
Clarification: For the production of blue cheese or Roquefort cheese, it is necessary to inoculate the curd with the microorganism, Penicillium roqueforti which brings about the necessary changes.

2. Pickled cucumber is made from fermented salt-stock pickles.
A. True
B. False
Answer: B
Clarification: Most commercial sweet, sour, mixed pickles are made from fermented salt-stock pickles. The other major type of pickled cucumber is the fermented dill pickle.

3. Bacterial cell grown on hydrocarbon wastes from the petroleum industry are a source of _____________
A. carbohydrates
B. proteins
C. vitamins
D. fats
Answer: B
Clarification: The microorganisms can be cultivated on industrial wastes or by-products as nutrients and yield a large cell crop that is rich in protein. Bacterial cell grown on hydrocarbon wastes from the petroleum industry are a source of protein in France, Japan, Taiwan, and India.

4. Yeast-cell crops harvested from the vats are used to produce which of the following compounds?
A. alcoholic beverages
B. enzymes
C. antibiotics
D. organic acids
Answer: A
Clarification: Yeast-cell crops harvested from the vats used to produce alcoholic beverages have been used as a food supplement for generations.

5. How many tons of protein can be produced by algae grown in pond in a year?
A. 1000
B. 1
C. 50
D. 20
Answer: D
Clarification: Algae grown in ponds can produce 20 tons (dry weight) of protein per acre per year.

6. What is the range of protein content in yeast cells?
A. 69%
B. 12-15%
C. 20-40%
D. 40-50%
Answer: D
Clarification: The protein content of microbial cells is very high. Yeast cells have a protein content in a 40 to 50 percent range.

7. Which of the following microorganism have high vitamin content?
A. bacteria
B. yeast
C. algae
D. protozoa
Answer: B
Clarification: Some microorganisms, particularly yeasts, have a high vitamin content. The growth medium for yeast cells consists of hydrocarbons supplemented with mineral salts.

8. The principal microorganism for yogurt is ______________________
A. Streptococcus thermophilus
B. Leuconostoc citrovorum
C. Lactobacillus acidophilus
D. Streptococcus lactis
Answer: A
Clarification: Streptococcus thermophilus and Lactobacillus bulgaricus are among the principal microorganisms responsible for producing yogurt by fermentation.

9. Which of the following products have higher acidity and lacks aroma?
A. Cultured buttermilk
B. Cultured sour cream
C. Bulgarian milk
D. Acidophilus milk
Answer: C
Clarification: For production of Bulgarian milk by Lactobacillus bulgaricus, incubation of inoculated milk at 37 degree C is carried out and the product differs from commercial buttermilk in having higher acidity and lacking aroma.

10. Shredded cabbage is the starting product for which of the following fermented food?
A. Sauerkraut
B. Pickles
C. Green olives
D. Sausage
Answer: A
Clarification: Shredded cabbage acts as a starting product for producing fermented product sauerkraut. Enterobacter cloacae is used in the early stage of fermentation.

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Microbiology Assessment Questions and Answers focuses on “Bacteria – Diseases Caused by Aerobic and Anaerobic Gram – Negative Rods”.

1. Syphilis is caused by which of the following organism?
A. Treponema pallidum
B. Treponema pertenue
C. Treponema endemicum
D. Treponema carateum
Answer: A
Explanation:Treponema pallidum causes syphilis disease in humans which is a venereal or congenital disease in humans.

2. Which of the following terms stand for damage to the spinal cord during tertiary stage of syphilis?
A. Lymphadenopathy
B. Malaise
C. Paresis
D. Tabes dorsalis
Answer: D
Clarification: Tabes dorsalis results from damage to the spinal cord: the patient becomes uncoordinated and has loss of reflexes, uncontrollable urination, loss of perception, and sensation, blindness and loss of hearing.

3. Which of the following is a specific test for detecting antitreponemal antibodies?
A. VDRL
B. RPR
C. TPH
D. Widal Test
Answer: C
Clarification: Two widely used specific tests are the fluorescent treponemal antibody (FTA. and the T. pallidum hemagglutination (TPH) test.

4. In which body part does the C. jejuni causes infection?
A. mouth
B. stomach
C. small and large intestine
D. limbs
Answer: C
Clarification: C. jejuni causes acute exudative and hemorrhagic inflammation of the wall of the small and large intestine.

5. Which disease is caused by P. pseudomallei organism?
A. melioidosis
B. diarrhea
C. gastroenteritis
D. typhoid
Answer: A
Clarification: P. pseudomallei are a tropical and subtropical soil organism that can cause a disease known as melioidosis in a large variety of animals and occasionally in humans.

6. Which of the following antibiotics is most effective?
A. streptomycin
B. tetracycline
C. gentamicin
D. ampicillin
Answer: C
Clarification: P.aeruginosa is resistant to many common antibiotics, although gentamicin and carbenicillin often are effective.

7. Pontiac fever is a more severe disease than Legionnaires’ disease.
A. True
B. False
Answer: B
Clarification: Pontiac fever is a less severe disease characterized by fever, chills, headache, dry cough and muscle pain and is self limiting and nonfatal.

8. Which of the following microorganism occurs in swine?
A. Brucella melitensis
B. Brucella abortus
C. Brucella suis
D. Legionella pneumophila
Answer: C
Clarification: Brucella suis occurs in swine. They are mainly parasites and pathogens of domestic animals.

9. Which drug is used for the treatment of brucellosis in humans?
A. Erythromycin
B. Tetracycline
C. Carbenicillin
D. Gentamicin
Answer: B
Clarification: Tetracycline is the drug of choice for the treatment of brucellosis in humans. No vaccine is available for human immunization.

10. The organism causing whooping cough can grow on ordinary culture media.
A. True
B. False
Answer: B
Clarification: The organism will not grow on ordinary culture media because such media contain toxic substances such as unsaturated fatty acids. Starch must be added to absorb these toxic substances.

11. Which of the following capsular polysaccharides is used for preparing a vaccine against meningococcal meningitis?
A. serovar A
B. serovar B
C. serovar C
D. serovar A and C
Answer: D
Clarification: A vaccine is available for epidemic control of meningococcal meningitis and consists of the purified capsular polysaccharides of serovars A and C; the serovar B polysaccharide appears not to be highly immunogenic.

12. Thayer-Martin medium is used for isolation of organism for which disease?
A. diphtheria
B. meningococcal meningitis
C. gonorrhea
D. gastroenteritis
Answer: C
Clarification: In the laboratory diagnosis of gonorrhea, isolation is done on Thayer-Martin medium, a rich blood-containing agar to which are added antibiotics to suppress the growth of other bacteria.

13. Which of the following strains causes acute gastroenteritis in newborns and infants?
A. Enteropathogenic strains
B. Enteroinvasive strains
C. Enterotoxigenic strains
D. Both enteropathogenic and enterotoxigenic
Answer: A
Clarification: Enteropathogenic strains colonize the jejunum and upper ileum of the small intestine and cause acute gastroenteritis in newborns and in infants.

To practice all areas of Microbiology Assessment Questions, .