Category: MICROBIOLOGY Objective Questions

Microbiology Questions and Answers for Experienced people focuses on “Utilization of Energy in Nonbiosynthetic Processes”.

1. Which of the following has no detectable ATPase activity?
A. cilia
B. eukaryotic flagella
C. bacterial flagella
D. endoflagella
Answer: C
Clarification: Bacterial flagella appears to have no machinery for interconverting chemical and mechanical energy. Flagellin, the flagellar protein molecule, has no enzymatic activity i.e. no detectable ATPase activity.

2. Which force drives the flagellar rotation in bacteria?
A. ATP
B. protonmotive force
C. electrons
D. water gradient
Answer: B
Clarification: The flagellar motor is driven by the protonmotive force, i.e., the force derived from the electric potential and the hydrogen gradient across the cytoplasmic membrane and not ATP.

3. Rotary motor of flagella is associated with _________
A. M ring
B. P ring
C. L ring
D. M and S ring
Answer: D
Clarification: The rotary motor is believed to be the two elements in the basal body, the M ring and the S ring. The rod (which is connected to the filament by the hook) is fixed rigidly to the M ring, which rotates freely in the cytoplasmic membrane. The S ring is mounted rigidly on the cell wall.

4. Passive diffusion requires the use of membrane transport proteins for the transport of solute molecules across the membrane.
A. True
B. False
Answer: B
Clarification: In passive diffusion no substance in the membrane interacts specifically with the solute molecules. The difference in concentration gradient governs the rate of the inward flow of solute molecules.

5. The entry of glycerol into the bacterial cells is by ____________
A. passive diffusion
B. facilitated diffusion
C. group translocation
D. active diffusion
Answer: B
Clarification: The entry of glycerol into the bacterial cells is an example of facilitated diffusion which involves the use of a specific protein carrier molecule called a porter for the diffusion of solutes.

6. Porter or permease is located in the _______________
A. cytoplasmic membrane
B. cell membrane
C. nuclear membrane
D. outer membrane
Answer: A
Clarification: Porter or permease is a specific protein carrier molecule that is required in facilitated diffusion which combines reversibly with the solute molecules and releases it into the inside of cell.

7. Facilitated diffusion does not require metabolic energy.
A. True
B. False
Answer: A
Clarification: Both the passive diffusion and facilitated diffusion does not require metabolic energy.

8. The reaction for the transfer of phosphoryl group of phosphoenol pyruvate to the sugar molecule requires which ion?
A. Mg²⁺
B. Fe²⁺
C. O
D. PO₄^2-
Answer: A
Clarification: The reaction for the transfer of phosphoryl group of phosphoenol pyruvate to the sugar molecule requires Mg²⁺, the products formed are sugar phosphate and pyruvate.

9. HPr stands for ______________
A. heat-stable carrier protein
B. hydrogen carrier protein
C. pyruvate dehydrogenase
D. high-energy protein
Answer: A
Clarification: Heat-stable protein (HPr) is activated first by transfer of phosphate group from the high-energy compound phosphoenol pyruvate inside the cell.

10. In phosphotransferase system(PTS), the sugar-phosphate is released inside the cell by which of the following?
A. Enzyme I
B. Enzyme II
C. Enzyme III
D. HPr
Answer: B
Clarification: Enzyme II is specific for a particular sugar, and is an integral component of the cytoplasmic membrane. Here it combines with the phosphate group carried by the activated HPr.The sugar-phosphate is released by enzyme II and enters the cell.

11. Mannitol enzyme II has been purified from _____________
A. E.coli
B. Salmonella typhimurium
C. Saccharomyces cerevisiae
D. Lactobacillus
Answer: A
Clarification: Mannitol enzyme II has been purified from E.coli. Other enzymes can be purified from several other bacteria.

To practice all areas of Microbiology for Experienced people, .

Microbiology Multiple Choice Questions on “Physiology and Cultivation of Fungi”.

1. Pathogenic fungi have a temperature optimum at __________
A. 30 to 37 degree celsius
B. 22 to 30 degree celsius
C. 37 to 42 degree celsius
D. 42 to 50 degree celsius
Answer: A
Clarification: Fungi grow over a wide range of temperatures. Pathogenic species have a higher temperature optimum, generally 30 to 37 degree Celsius.

2. Sabouraud media for the growth of fungi is composed of ____________________
A. glucose and ammonia
B. maltose and peptone
C. sucrose and peptone
D. peptone
Answer: B
Clarification: One of the best known and oldest media for the growth of fungi is Sabouraud media that contains maltose and peptone as its principal ingredients.

3. Sabouraud media has ________________
A. high ph, low sugar concentration
B. high ph, moderate sugar concentration
C. low ph, high sugar concentration
D. low ph, moderate sugar concentration
Answer: C
Clarification: Sabouraud media is widely used for the isolation of molds and certain yeasts. Its partial selective action is due to the high sugar concentration and low pH.

4. Jams and jellies are spoiled by both bacteria and fungi.
A. True
B. False
Answer: B
Clarification: Yeasts and molds can grow in a substrate or medium containing concentrations of sugars that inhibit most bacteria; this is why jams and jellies may be spoiled by molds but not by bacteria.

5. What are the cell wall structural components of fungi?
A. peptidoglycan
B. cellulose
C. chitin
D. chitin,cellulose, or hemicellulose
Answer: D
Clarification: The cell wall structural components of fungi are chitin, cellulose, or hemicellulose whereas the bacterial cell wall is composed of peptidoglycan.

6. The optimum pH for the growth of fungi is ____________
A. 7.8-9.0
B. 12-14
C. 3.8-5.6
D. 1.0-2.0
Answer: C
Clarification: The optimum pH for the growth of fungi is 3.8-5.6. Acidic media (pH 5.6) are tolerated by molds but are inhibitory to most bacteria.

7. Which of the following are the oxygen requirements of molds?
A. Strictly aerobic
B. Facultatively aerobic
C. Anaerobic
D. Microaerophilic
Answer: A
Clarification: Moulds are strictly aerobic whereas yeasts are facultative organisms.

8. Fungi are sensitive to which of the following antibiotics?
A. penicillins
B. tetracyclins
C. chloramphenicol
D. griseofulvin
Answer: D
Clarification: Fungi are resistant to penicillins, tetracyclins, chloramphenicol but are sensitive to griseofulvin.

9. Ordinary inoculating loop can be used for inoculation of yeasts.
A. True
B. False
Answer: A
Clarification: Ordinary inoculating loop used for bacteria is suitable for the inoculation of yeasts. But the needle used for molds is stiffer and has a flattened tip for cutting the mycelium.

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Microbiology MCQs focuses on “Virus Infection and Fatal Diseases Associated with Viruses in Animals”.

1. Which of the following inclusion bodies are present in the cytoplasm of the Purkinje cells of the cerebellum in the case of rabies infection?
A. Paschen bodies
B. Guarnieri bodies
C. Negri bodies
D. Elementary bodies
Answer: C
Clarification: Characteristic inclusion bodies are found in the cytoplasm of the Purkinje cells of the cerebellum and in certain other nerve cells in cases of rabies infection. These typical inclusion bodies are Negri bodies and is diagnostic of the disease.

2. Bollinger bodies are found in the cytoplasm of cells infected by which of the following viruses?
A. variola virus
B. fowl pox virus
C. rabies virus
D. herpes virus
Answer: B
Clarification: Bollinger bodies are found in the cytoplasm of cells infected with fowl pox virus. It is a type of inclusion body produced by viruses in certain host tissues.

3. Intracytoplasmic inclusions are found in chicken pox, herpes, and the polyhedra diseases of insects.
A. True
B. False
Answer: B
Clarification: Intranuclear inclusions are found in chicken pox, herpes, and the polyhedra diseases of insects. Intranuclear and intracytoplasmic inclusions may be found in the same cell in instances of multiple infections.

4. Scrapie is a chronic disease of which of the following animals?
A. sheep
B. mouse
C. mink
D. cow
Answer: A
Clarification: Scrapie is so named because the diseased animal tends to scrape against fixed objects. It is a chronic infection of the central nervous system of sheep.

5. In which of the following categories of cancer solid tumors grow from derivatives of embryonal mesoderm?
A. Leukemias
B. Lymphomas
C. Sarcomas
D. Carcinomas
Answer: C
Clarification: In Sarcoma solid tumors grow from derivatives of embryonal mesoderm, such as connective tissues, cartilage, bone, muscle and fat.

6. Anaplasia is structural abnormality of cells.
A. True
B. False
Answer: A
Clarification: Cancer has three major characteristics: hyperplasia, anaplasia, and metastasis. Anaplasia is structural abnormality of cells (these cells also have a loss of or reduction in their functions).

7. Which among the following is the family of RNA containing viruses that can cause cancer in animals?
A. Herpesviridae
B. Adenoviridae
C. Papovaviridae
D. Retroviridae
Answer: D
Clarification: Among the viruses whose virions contain RNA, only some members of the family Retroviridae cause cancer in animals. These members replicate through a DNA intermediate.

8. Cancer of the lip of mouth have been associated with ___________
A. HSV1
B. HSV2
C. EBV
D. SV 40
Answer: A
Clarification: HSV1 is a herpes virus type 1 which is associated with the cancer of the lip of the mouth in humans wheras HSV2 causes cervical cancer.

9. The Epstein-Barr virus (EBV) can induce tumors in _____________
A. mouse
B. monkey
C. humans
D. rodents
Answer: C
Clarification: The Epstein-Barr virus (EBV), a herpesvirus, has been consistently associated with certain human neoplasias, or tumors.

To practice MCQs on all areas of Microbiology, .

Microbiology Multiple Choice Questions on “Wastewater and Treatment Processes”.

1. Which of the following sewerage systems carry domestic and industrial wastewater?
A. sanitary sewers
B. storm sewers
C. combined sewers
D. storm and combined sewers
Answer: A
Clarification: Sanitary sewers carry domestic and industrial wastewater for its ultimate treatment and disposal.

2. The more oxidizable organic material, the lesser the BOD.
A. True
B. False
Answer: B
Clarification: The magnitude of the BOD is related to the amount of organic material in the wastewater-i.e., the more oxidizable organic material, the higher the BOD.

3. Which of the following is a strict anaerobe?
A. Enterobacter
B. Alcaligenes
C. Pseudomonas
D. Methanosarcina
Answer: D
Clarification: Methane producers are strict anaerobes e.g., Methanobacterium, Methanosarcina, Methanococcus. They produce methane and carbon dioxide as end products.

4. In which of the following treatment involve oxidation of organic constituents of the wastewater?
A. Primary treatment
B. Secondary treatment
C. Advanced treatment
D. Final treatment
Answer: B
Clarification: Secondary or biological treatment is done to adsorb and ultimately oxidize organic constituents of the wastewater, i.e, to reduce the BOD.

5. The upper region of the trickling filter is favorable for the growth of _____________
A. fungi
B. protozoa
C. algae
D. bacteria
Answer: C
Clarification: The upper region of the trickling filter is favorable for the growth of algae, and at times their growth may become so extensive that it impairs the operation of the filter.

6. Activated sludge usually employs an aeration period of ________________
A. 1 hour
B. 24 hours
C. 10-15 hours
D. 4-8 hours
Answer: D
Clarification: The activated sludge process usually employs an aeration period of 4 to 8 hours, after which the mixture is piped to a sedimentation tank.

7. Oxidation ponds are very deep ponds.
A. True
B. False
Answer: B
Clarification: Oxidation ponds also called lagoons are shallow ponds which are 2 to 4 ft in depth designed to allow algal growth on the wastewater effluent.

8. Trickling filter is used in which of the following wastewater treatment processes?
A. Primary treatment
B. Secondary treatment
C. Advanced treatment
D. Final treatment
Answer: B
Clarification: The trickling filter is used in secondary treatment in which a stationary microbial culture is fed by a continuous supply of nutrients. It is used for filtration processes.

9. Belt filter presses are used in which of the following process?
A. Thickening
B. Stabilization
C. Dewatering
D. Disposal
Answer: C
Clarification: Dewatering is done by vacuum filters, belt filter presses and centrifuges and is often enhanced by the addition of polymer or other chemical coagulant aids.

10. Which of the following gases are produced in large amounts during sludge digestion?
A. methane
B. carbon-dioxide
C. hydrogen
D. nitrogen
Answer: A
Clarification: About 60-70% methane is produced during sludge digestion with smaller amounts of carbon dioxide, hydrogen and nitrogen.

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Microbiology Multiple Choice Questions on “Infection Process – Penetration of Epithelial Cell Layers”.

1. Which of the following microorganism causes infection in burns?
A. Pseudomonas aeruginosa
B. Clostridium perfringens
C. Borrelia sp
D. Streptococcus sp
Answer: A
Clarification: 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
Answer: A
Clarification: 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.
Answer: C
Clarification: 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
Answer: B
Clarification: 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
Answer: B
Clarification: 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
Answer: C
Clarification: 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
Answer: A
Clarification: 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
Answer: B
Clarification: Arthropods follow passive penetration such as that by Borrelia species which causes relapsing fever in humans.

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Microbiology Multiple Choice Questions on “Morphology and Fine Bacteria Structure – Cell Wall”.

1. Peptidoglycan layer is present in large quantity in?
A. Gram-positive bacteria
B. Gram-negative bacteria
C. Fungi
D. Algae
Answer: A
Clarification: Gram-positive bacteria usually have a much greater amount of peptidoglycan in their cell walls than do Gram-negative bacteria. It may account for 50 percent or more of the dry weight of the wall of some Gram-positive species, but only about 10 percent of the wall of Gram-negative bacteria.

2. Peptidoglycan is made up of __________
A. N-acetylglucosamine
B. N-acetylmuramic acid
C. N-acetylglucosamine, N-acetylmuramic acid
D. N-acetylglucosamine, N-acetylmuramic acid, amino acids
Answer: D
Clarification: Peptidoglycan differs somewhat in composition and structure from one species to another, but it is basically a polymer of N-acetylglucosamine, N-acetylmuramic acid, Amino acids like-L-alanine, D-alanine, D-glutamate, and a diamino acid.

3. Teichoic acid present in Gram-positive bacteria can bind to which ion?
A. Fe ions
B. Phosphorus ions
C. Mg ions
D. Sulphur ions
Answer: C
Clarification: Teichoic acid bind magnesium ions and there is some evidence that they help to protect bacteria from thermal injury by providing an accessible pool of these cations for stabilization of the cytoplasmic membrane.

4. Cord factor is a ___________
A. protein
B. teichoic acid derivative
C. mycolic acid derivative
D. carbohydrate
Answer: C
Clarification: Cord factor (trehalose dimycolate) is a mycolic acid derivative which is toxic and plays an important role in the diseases caused by C.diphtheriae and M.tuberculosis.

5. The outer membrane of the Gram-negative cell wall is anchored to the underlying peptidoglycan by means of which of the following?
A. Braun’s Lipoprotein
B. Phospholipids
C. Proteins
D. Lipopolysaccharide
Answer: a
Clarification: The outer membrane of the Gram-negative cell wall is anchored to the underlying peptidoglycan by means of Braun’s lipoproteins. The membrane is a bilayered structure consisting mainly of phospholipids, proteins and lipopolysaccharides(LPS).

6. Which among the following acts as receptors for bacteriophage attachment in Gram-negative bacteria?
A. Cilia
B. O antigens
C. Lipid A
D. Teichoic acid
Answer: B
Clarification: The polysaccharide O antigens which extend like whiskers from the membrane surface into the surrounding medium. Many of the serological properties of Gram-negative bacteria are attributable to O antigens like they can serve as receptors for bacteriophage attachment.

7. Porins are special proteins act as channels in the outer membrane of Gram-negative bacteria.
A. True
B. False
Answer: A
Clarification: The outer membrane can allow smaller molecules such as nucleosides, oligosaccharides, monosaccharides, peptides and amino acids to pass across by means of channels in special proteins called porins.

8. NAG and NAM of peptidoglycan layer is linked by _________
A. beta-(1,4) glycosidic linkage
B. alpha-(1,4) glycosidic linkage
C. alpha-(1,6) glycosidic linkage
D. beta-(1,6) glycosidic linkage
Answer: A
Clarification: N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) of peptidoglycan layer are linked by beta-(1, 4) glycosidic linkage. Each strand contains from 10 to 65 disaccharide units.

9. Gram-negative bacteria are more resistant to antibiotics due to the presence of?
A. Thin peptidoglycan wall
B. Outer lipopolysaccharide layer
C. Porin proteins
D. Teichoic acid
Answer: B
Clarification: Gram-negative bacteria consists of an outer membrane made up of lipopolysaccharides beneath the thin peptidoglycan layer. The outer membrane serves as a barrier to various external chemicals and enzymes that could damage the cell. It also protects the bacteria from antibiotics.

10. Which of the following are present in teichoic acids?
A. ribitol residues
B. glycerol residues
C. glucose residues
D. ribitol or glycerol residues
Answer: D
Clarification: The teichoic acids are water soluble polymers, containing ribitol or glycerol residues joined through phosphodiester linkages. The glycerol or ribitol is joined to a sugar residue such as glucose, galactose or N-acetyl glucosamine.

11. Bayer’s junctions are sites which help in joining which of the following?
A. cytoplasmic membrane and outer membrane
B. outer membrane and capsule
C. cytoplasmic membrane and periplasmic space
D. peptidoglycan layer and cytoplasmic membrane
Answer: A
Clarification: The cytoplasmic membrane and outer membrane are joined at sites termed Bayer’s junctions. In these regions, the outer surface of the cytoplasmic membrane is continuous with the inner surface of the outer membrane creating pores that vary in diameter from 25 to 50 nm.

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