Sem 3 BRS Micro - General Properties Of Microorganisms; /Bacteria

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Sem 3 BRS Micro - General Properties Of Microorganisms; /Bacteria - Quiz


Questions and Answers
  • 1. 

    A pharmaceutical company has developed a new compound that is well tolerated by the body and inhibits the sterol ergo sterol synthesis. Screening of anti-infectious agent activity should be directed toward

    • A.

      Bacteria

    • B.

      Chlamydia species

    • C.

      Fungi

    • D.

      Rickettsia species

    • E.

      Viruses

    Correct Answer
    C. Fungi
    Explanation
    Fungi have ergo sterol as their dominant membrane sterol. Mycoplasmas are the only prokaryotes with sterols in their cytoplasmic membrane, but they do not synthesize their own sterols.

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  • 2. 

    50S ribosomal subunits are found in

    • A.

      Bacteria

    • B.

      Fungi

    • C.

      Prions

    • D.

      Protozoa

    • E.

      Viruses

    Correct Answer
    A. Bacteria
    Explanation
    Bacteria have70S ribosomes composed of 30S and 50S subunits. Fungi and protozoa have 80S ribosomes, and prions and viruses do not have ribosomes.

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  • 3. 

    The normal flora of the large intestine consists mainly of

    • A.

      Bacteria

    • B.

      Fungi

    • C.

      Protozoa

    • D.

      Viruses

    • E.

      No microbial agents

    Correct Answer
    A. Bacteria
    Explanation
    Bacteria form the majority of the normal flora of the large intestine. Other types of human infectious agents are not usually present except in time of disease.

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  • 4. 

    The minimal concentration of alcohol necessary to kill bacteria and enveloped viruses is

    • A.

      30%

    • B.

      40%

    • C.

      50%

    • D.

      60%

    • E.

      70%

    Correct Answer
    E. 70%
    Explanation
    An alcohol concentration of 70% to 95% is necessary to kill bacteria

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  • 5. 

    Human obligate intracellular pathogens that depend on the host cell for ATP production are

    • A.

      Bacteriophages

    • B.

      Mycoplasma species

    • C.

      Prions

    • D.

      Rickettsia species

    • E.

      Viroids

    Correct Answer
    D. Rickettsia species
    Explanation
    Chlamydia and rickettsia are obligate intracellular pathogens because they depend on the host cell
    to provide them with ATP.

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  • 6. 

    Dimorphism is a characteristic of

    • A.

      Bacteria

    • B.

      Fungi

    • C.

      Prions

    • D.

      Rickettsia species

    • E.

      Viruses

    Correct Answer
    B. Fungi
    Explanation
    Certain species of pathogenic fungi are dimorphic (i.e., existing as yeast or mold forms depending
    on their environment).

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  • 7. 

    A new infectious agent has been isolated from deer ticks. It lacks a cell wall but has 70S ribosomes. This agent is most likely a

    • A.

      Bacterium

    • B.

      Chlamydia species

    • C.

      Mycoplasma species

    • D.

      Rickettsia species

    • E.

      Virus

    Correct Answer
    C. Mycoplasma species
    Explanation
    The correct answer is Mycoplasma species. Mycoplasma species are unique bacteria that lack a cell wall, making them resistant to antibiotics that target cell wall synthesis. They also have 70S ribosomes, which are characteristic of bacteria. Chlamydia species and Rickettsia species are also bacteria, but they have cell walls. Viruses are not considered bacteria and do not possess ribosomes.

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  • 8. 

    Chapter 2 BACTERIA A bacterial toxin with super antigen activity is produced by

    • A.

      Clostridia tetani

    • B.

      Bordetella pertussis

    • C.

      Escherichia coli

    • D.

      Staphylococcus aureus

    • E.

      Vibrio cholera

    Correct Answer
    D. Staphylococcus aureus
    Explanation
    Staphylococcus aureus produces an enterotoxin and TSST-1 toxins with super-antigen activity.
    Streptococcus pyogenes also produces toxins with this activity.

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  • 9. 

    Sugar transport into bacteria is frequently facilitated by

    • A.

      Acetyl transferase

    • B.

      Neuraminidases

    • C.

      Oxidases

    • D.

      Penicillin-binding proteins

    • E.

      Phospho transferases

    Correct Answer
    E. Phospho transferases
    Explanation
    The transport of sugar into a bacterium frequently involves the transfer of a phosphate group to the s
    ugar molecule.

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  • 10. 

    Thayer-Martin and Martin-Lewis media are used to isolate and identify E. coli

    • A.

      E. coli

    • B.

      Mycobacteria

    • C.

      Neisseria

    • D.

      Salmonella

    • E.

      Shigella

    Correct Answer
    C. Neisseria
    Explanation
    These media are variants of chocolate agar and contain antibiotics that inhibit many normal respiratory
    and genital bacteria but allow the growth of Neisseria species.

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  • 11. 

    B-lactamases confer antibiotic resistance by

    • A.

      Altering antibiotic permeability

    • B.

      Altering penicillin-binding proteins

    • C.

      Altering 70S ribosome structure

    • D.

      Modifying cellular RNA polymerase

    • E.

      Modifying antibiotic structure

    Correct Answer
    E. Modifying antibiotic structure
    Explanation
    B-lactamases cleave the b-lactam ring structure that is important for the antibacterial activity of penicillins,
    cephalosporins, monobactams, and carbapenems.

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  • 12. 

    Polymers of N-acetyl glucosamine and N-acetyl  muramic acid are found in which of the following structures?

    • A.

      Teichoic acid

    • B.

      Cell wall

    • C.

      Glycocalyx

    • D.

      Lipopolysaccharide

    Correct Answer
    B. Cell wall
    Explanation
    N-acetyl glucosamine and N-acetyl muramic acid are polymerized to form the peptidoglycan backbone of the cell wall.

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  • 13. 

    A phage that is not inactivated by proteases is called a

    • A.

      Prophage

    • B.

      Virulent phage

    • C.

      Temperate phage

    • D.

      Filamentous phage

    Correct Answer
    A. Prophage
    Explanation
    A prophage is the intracellular DNA of a phage and is therefore resistant to protease degradation.

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  • 14. 

    Bacteria that synthesize organic compounds from inorganic compounds are

    • A.

      Heterotrophs

    • B.

      Obligate anaerobes

    • C.

      Aerobes

    • D.

      Facultative anaerobes

    • E.

      Autotrophs

    Correct Answer
    E. Autotrophs
    Explanation
    Autotrophic bacteria do not require organic compounds for growth because they synthesize them
    from inorganic precursors.

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  • 15. 

    A bacterial structure involved in adherence is

    • A.

      Capsule

    • B.

      Lipopolysaccharide

    • C.

      Ordinary pili

    • D.

      O-specific side-chain

    • E.

      Teichoic acid

    Correct Answer
    C. Ordinary pili
    Explanation
    Ordinary pili, adhesins, and the glycocalyx are three bacterial structures that are involved in adherence.

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  • 16. 

    Aminoglycoside antibiotics are

    • A.

      Bactericidal for Gram-positive bacteria

    • B.

      Inactivated by R-factor phosphor transferases

    • C.

      Mycolic acid synthesis inhibitors

    • D.

      Peptidoglycan synthesis inhibitors

    • E.

      Require bacterial growth for the effect

    Correct Answer
    E. Require bacterial growth for the effect
    Explanation
    Bacteria must be actively replicating and synthesizing protein for these compounds, which bind
    to the 30S ribosomal subunit to have their bactericidal effect.

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  • 17. 

    A-B subunit structure as it relates to bacterial pathogenesis refers to the structure of

    • A.

      Bacterial exotoxins

    • B.

      Gram-negative bacteria endotoxin

    • C.

      Nucleic acid inhibitor antibiotics

    • D.

      Penicillin-binding proteins

    • E.

      Resistance transfer factors

    Correct Answer
    A. Bacterial exotoxins
    Explanation
    Many bacterial exotoxins have an A-B subunit structure in which the B subunit is involved in binding
    and the A subunit possesses biological activity inside the affected cell.

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  • 18. 

    Which of the following displays the Pasteur effect?

    • A.

      Heterotrophs

    • B.

      Obligate anaerobes

    • C.

      Aerobes

    • D.

      Facultative anaerobes

    • E.

      Autotrophs

    Correct Answer
    D. Facultative anaerobes
    Explanation
    Facultative anaerobes shift from a fermentative to a respiratory metabolism in the presence of
    air because the energy needs of the cell are met by consuming less glucose (Pasteur Effect) under respiratory metabolism.

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  • 19. 

    Which of the following toxins acts on synaptosomes?

    • A.

      E. coli heat-labile toxin

    • B.

      Clostridium tetani exotoxin

    • C.

      Corynebacterium diphtheria exotoxin

    • D.

      Pseudomonas aeruginosa exotoxin

    • E.

      Clostridium perfringens alpha-toxin

    Correct Answer
    B. Clostridium tetani exotoxin
    Explanation
    Clostridium tetani Exotoxin acts on synaptosomes, thereby causing hyper-reflexia of skeletal muscles.

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  • 20. 

    Superoxide dismutase-containing bacteria

    • A.

      Need superoxide to grow

    • B.

      Are frequently obligate anaerobes

    • C.

      Grow slowly in the presence of CO2

    • D.

      Produce hydrogen peroxide from hydrogen ion and the superoxide free radical (O2-)

    Correct Answer
    D. Produce hydrogen peroxide from hydrogen ion and the superoxide free radical (O2-)
    Explanation
    Superoxide dismutase is found in aerobic and facultative anaerobic bacteria. It protects them from
    the toxic free radical (O2-) by combining it with a hydrogen ion to form hydrogen peroxide, which is
    subsequently degraded by peroxidase.

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  • 21. 

    Lysogenic phage conversion involves

    • A.

      The transformation of a virulent phage to a lysogenic phage

    • B.

      A change in bacterial phenotype due to the presence of a prophage

    • C.

      The conversion of a prophage to a temperate phage

    • D.

      The incorporation of a prophage into the bacterial chromosome

    Correct Answer
    B. A change in bacterial phenotype due to the presence of a prophage
    Explanation
    Lysogenic phage conversion refers to the process in which a bacterial phenotype changes as a result of the presence of a prophage. A prophage is a viral genome that has integrated into the bacterial chromosome and remains dormant until it is activated. When the prophage is activated, it can cause changes in the bacterial phenotype, such as the production of toxins or other virulence factors. This change in phenotype is the result of the expression of genes carried by the prophage, which can alter the behavior or characteristics of the bacterial host.

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  • 22. 

    Bacteria capable of growth in a high salt concentration are best isolated in which of the following media?

    • A.

      Minimal growth media

    • B.

      Complex growth media

    • C.

      Differential growth media

    • D.

      Selective growth media

    Correct Answer
    D. Selective growth media
    Explanation
    A selective growth medium that contains a high salt concentration would permit bacterial growth.

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  • 23. 

    Bacteria lacking superoxide dismutase are

    • A.

      Heterotrophs

    • B.

      Obligate anaerobes

    • C.

      Aerobes

    • D.

      Facultative anaerobes

    • E.

      Autotrophs

    Correct Answer
    B. Obligate anaerobes
    Explanation
    Superoxide dismutase, which is present in aerobes and facultative anaerobe organisms, protects them
    from the toxic O2- radical. This enzyme is not present in obligate anaerobes.

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  • 24. 

    The regulation of enzyme activity in bacterial cells can

    • A.

      Be coupled to the binding of effector molecules

    • B.

      Be controlled by a catabolite activator protein(CAP)

    • C.

      Occur via attenuation sequences

    • D.

      Involve inducer molecules

    Correct Answer
    A. Be coupled to the binding of effector molecules
    Explanation
    The biochemical activity of an enzyme may be regulated by binding of effect or molecules or by
    biosynthetic pathway end-product feedback inhibition. Enzyme synthesis may be controlled by inducers,
    attenuation sequences, or catabolite activator protein.

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  • 25. 

    The plasma membrane

    • A.

      Contains matrix porins

    • B.

      Includes endotoxin

    • C.

      Contains glycocalyx

    • D.

      Contains the enzymes involved in bacterial oxidative phosphorylation

    Correct Answer
    D. Contains the enzymes involved in bacterial oxidative phosphorylation
    Explanation
    The plasma membrane contains the enzymes involved in oxidative phosphorylation

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  • 26. 

    Bacterial antibiotic resistance is frequently conveyed by

    • A.

      A temperate bacteriophage

    • B.

      An R-factor plasmid

    • C.

      A replicon

    • D.

      A lytic bacteriophage

    • E.

      An intron

    Correct Answer
    B. An R-factor plasmid
    Explanation
    R-factor (resistance) plasmids contain genes for proteins that degrade antibiotics or alter antibiotic
    transport, thus conferring antibiotic resistance. They also carry transfer genes, which facilitate their
    intercellular transfer to other genomes.

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  • 27. 

    The expression of the lac operon

    • A.

      Must be initiated by the binding of an inducer protein

    • B.

      Involves the release of allolactose from a repressor protein

    • C.

      Does not involve the expression of structural genes

    • D.

      Necessitates the finding of RNA polymerase followed by transcription

    Correct Answer
    A. Must be initiated by the binding of an inducer protein
    Explanation
    The transcription of the lac operon is under negative control. Initiation depends on the binding of
    allolactose to a repressor protein. This reaction prevents the repressor from binding to the operator
    region, thus allowing RNA polymerase to bind and transcription to proceed.

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  • 28. 

    Bacteriophage containing host-cell DNA is involved in which of the following processes?

    • A.

      Transformation

    • B.

      Conjugation

    • C.

      Transduction

    • D.

      Transcription

    • E.

      Recombination

    Correct Answer
    C. Transduction
    Explanation
    Bacteriophages containing portions of host-cell DNA can introduce this genetic material into new host cells via the process of transduction.

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  • 29. 

    The exchange of allelic forms of genes is involved in which of the following processes?

    • A.

      Transformation

    • B.

      Conjugation

    • C.

      Transduction

    • D.

      Transcription

    • E.

      Recombination

    Correct Answer
    E. Recombination
    Explanation
    DNA or genetic recombination is the general term used to describe the exchange of allelic forms
    of genes in bacteria or eukaryotic cells.

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  • 30. 

    Which of the following processes creates high-frequency recombination donors?

    • A.

      Transformation

    • B.

      Conjugation

    • C.

      Transduction

    • D.

      Transcription

    • E.

      Recombination

    • F.

      Translation

    Correct Answer
    E. Recombination
    Explanation
    High-frequency recombination donors, which result from the integration of a fertility (F) factor in to
    chromosomal DNA, are created by recombination.

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  • Current Version
  • Jan 18, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Jun 04, 2012
    Quiz Created by
    Rosssweetie
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