Category: MICROBIOLOGY Objective Questions

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.

.

Microbiology Multiple Choice Questions on “Utilization of Energy in Biosynthetic Processes”.

1. The biosynthesis of proline takes place from ____________
A. aspartic acid
B. glutamic acid
C. pyruvic acid
D. alpha-keto glutaric acid
Answer: B
Clarification: The biosynthesis of proline takes place from glutamic acid in which the initial step utilizes metabolic energy in the form of ATP.

2. Which of the following acts as a precursor for the activation of peptidoglycan?
A. TP
B. UDP
C. NADPH
D. GTP
Answer: B
Clarification: Sugars such as acetylglucosamine are activated by the attachment of a UDP to form a sugar-UDP precursor which is a general method involved in the biosynthesis of peptidoglycan.

3. Bactoprenol is a ___________
A. membrane phospholipid
B. amino acid carrier
C. fatty acid
D. enzyme
Answer: A
Clarification: Bactoprenol is a membrane phospholipid to which the AMA-UDP precursor is coupled during the synthesis of peptidoglycan.

4. Electrons entering the respiratory chain of chemoautotrophic bacteria enter the chain at higher potential.
A. True
B. False
Answer: A
Clarification: Electrons entering the respiratory chain from the oxidation of inorganic substrates by chemoautotrophic bacteria usually enter the chain at a higher point than those electrons from the oxidation of organic substrates by chemoheterotrophs. Thus chemoautotrophs are at a considerable energetic disadvantage for this reason.

5. ATP dependent NADPH₂ production is a process found in ______________
A. Nitrosomonas
B. Nitrobacter
C. Rhizobium
D. E.coli
Answer: B
Clarification: Nitrobacter is a chemiautotrophic bacteria that follows the process of ATP-dependent-NADPH2 production for the production of NADPH2 to be used with ATP for carbon dioxide fixation.

6. Each turn of Calvin cycle results in the fixation of ________ molecule of carbon dioxide.
A. one
B. two
C. four
D. six
Answer: A
Clarification: Each turn of the Calvin cycle results in the fixation of one molecule of carbon dioxide. Carbon dioxide is fixed in a reaction with the acceptor molecule ribulose diphosphate.

7. The peptidoglycan layer of Staphylococcus aureus consists of a bridge between muramic acid peptides which is composed of?
A. alanine
B. lysine
C. proline
D. gycine
Answer: D
Clarification: In Staphylococcus aureus a bridge composed of five glycine molecules can link two muramic acid peptides together.

8. Binding proteins for active transport systems of Gram-negative bacteria are associated with ____________
A. cell membrane
B. cytoplasmic membrane
C. periplasmic space
D. nuclear membrane
Answer: C
Clarification: Active-transport of Gram-negative bacteria are associated with binding proteins in the periplasmic space. The binding proteins have very high affinities for specific nutrients, including amino acids, sugars, and inorganic ions.

.

Microbiology Multiple Choice Questions on “Classification of Fungi”.

1. In the fungal classification system Ascomycetes come under the division of ________________
A. Gymnomycota
B. Mastigomycota
C. Amastigomycota
D. Gymnomycota, Mastigomycota
Answer: C
Clarification: The class of Ascomycetes comes under the division of Amastigomycota which are terrestrial fungi.

2. Rhizopus stolonifer belongs to which class?
A. Acrasiomycetes
B. Zygomycetes
C. Ascomycetes
D. Deuteromycetes
Answer: B
Clarification: Rhizopus stolonifer belongs to the class Zygomycetes and division Amastigomycota.

3. Which class of fungi among the following have motile cells with two laterally inserted flagella, one tinsel and the other whiplash?
A. Chytridiomycetes
B. Zygomycetes
C. Deuteromycetes
D. Oomycetes
Answer: D
Clarification: The Oomycetes class have motile cells with two laterally inserted flagella, one tinsel and anteriorly directed, the other whiplash and posteriorly directed.

4. Which division of fungi lacks flagella?
A. Mastigomycota
B. Amastigomycota
C. Gymnomycota
D. Basidiomycetes
Answer: B
Clarification: The division Amastigomycota or terrestrial fungi lack flagella. Mainly sexual spores are produced by the organisms of this division.

5.Fruiting bodies of slime moulds are called ______________
A. acervulus
B. sori
C. apothecium
D. perithecium
Answer: B
Clarification: Fruiting bodies of slime moulds are called sori that are masses of spores.

6. The taxa having the ending -mycetes is _______________
A. Division
B. Subdivision
C. Class
D. Order
Answer: C
Clarification: Class have the ending-mycetes. Division have the ending -mycota, subdivision ends with -mycotina whereas order ends with -ales.

7. The common yeast Schizosaccharomyces follows which of the following asexual reproduction methods?
A. binary fission
B. budding
C. fragmentation
D. spore formation
Answer: A
Clarification: In Schizosaccharomyces, asexual reproduction is by binary fission. Sexual reproduction is by conjugation of compatible cells with the subsequent formation of ascospores.

8. The structure which contains the zygote nuclei in Rhizopus stolonifer is is known as _______________
A. progametangia
B. zygospore
C. suspensor cell
D. coenozygote
Answer: D
Clarification: The walls of the two contacting gametangia dissolve at the point of contact, the two protoplasts mix and the + and – nuclei fuse to form many zygote nuclei. The structure which contains them is called the coenozygote.

9. The mature zygospore lies dormant for how many days?
A. 4-5 days
B. 1-3 months
C. 1 year
D. 20 days
Answer: B
Clarification: The wall around the coenozygote thickens and its surface becomes black and warty, forming the mature zygospore, which lies dormant for 1 to 3 or more months.

10. Which of the following are acellular slime moulds?
A. Acrasiomycetes
B. Myxomycetes
C. Oomycetes
D. Ascomycetes
Answer: B
Clarification: Myxomycetes are acellular slime molds whose vegetative phase consists of a multicellular, wall-less plasmodium, which transforms into highly organized sporangia bearing sporangiospores.

.

Microbiology Multiple Choice Questions on “Microorganisms Control by Physical Agents – Fundamentals of Control”.

1. In which of the following situations will the logarithmic plot of survivors be constant?
A. physiological conditions are different
B. cells of microbial population vary in size
C. age and physiological conditions are uniform
D. temperature conditions are different
Answer: C
Clarification: Logarithmic plot reveals that the death rate is constant when all conditions are strictly uniform, including the age and the physiological condition of all the microorganisms in the population.

2. A suspension of E.coli exposed to heat treatment may yield a greater number of survivors if a plating medium of _____________ is used.
A. peptone
B. trypticase soy agar
C. deoxycholate agar
D. potato dextrose
Answer: B
Clarification: A suspension of E.coli exposed to heat treatment may yield a greater number of survivors if a plating medium of trypticase soy agar is used rather than a medium containing bile salts such as deoxycholate agar.

3. We require less time to kill the population of many cells.
A. True
B. False
Answer: B
Clarification: It takes time to kill the population and if we have many cells, we must treat them for a longer time to be reasonably sure that all of the bacteria are dead.

4. The effectiveness of heat in killing microorganisms is much greater in _____________
A. acid
B. alkali
C. neutral
D. acid and alkali
Answer: A
Clarification: The environment has a profound influence on the rate as well as the efficacy of microbial destruction. The effectiveness of heat is much greater in acid than in alkali material.

5. A high concentration of which of the following compounds in the material generally increases the thermal resistance of microorganisms?
A. proteins
B. carbohydrates
C. lipids
D. salts
Answer: B
Clarification: The consistency of the material will markedly influence the penetration of the agent and high concentration of carbohydrates generally increases the thermal resistance of organisms.

6. Which of the following show the maximum resistance to physical and chemical agents?
A. Viruses
B. Mold spores
C. Bacterial spores
D. E.coli
Answer: C
Clarification: In spore forming species, the bacterial spores are extremely resistant in comparison to growing vegetative cells to physical and chemical agents.

7. How much time is required by the young cells to be killed by a lethal agent?
A. 24 hours
B. 3-4 hours
C. 30 mins
D. 5 mins
Answer: C
Clarification: The young cells are all killed within 25 minutes but a considerable part of the more resistant, older cells still survives. Young, actively metabolizing cells are apt to be more easily destroyed than old, dormant cells.

8. Which of the following actions are not affected by antimicrobial agents?
A. cell wall synthesis
B. nucleic acid synthesis
C. protein synthesis
D. capsule formation
Answer: D
Clarification: Antimicrobial agents inhibit or kill microorganisms by any of these actions like damaging cell wall synthesis, inhibiting protein or nucleic acid synthesis and inhibition of enzyme action.

.

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.

.

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.

.