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Bacterial Classification Flashcards

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  1. Which bacterial structure is the primary target of the Gram stain procedure?

    Answer: Peptidoglycan cell wall

    The Gram stain differentiates bacteria based on the thickness of their peptidoglycan cell wall.

  2. Bacteria classified as obligate anaerobes would be killed by exposure to which condition?

    Answer: Molecular oxygen

    Obligate anaerobes lack the enzymes needed to detoxify reactive oxygen species, so oxygen is lethal to them.

  3. Which of the following best describes the classification of Mycobacterium tuberculosis?

    Answer: Acid-fast bacillus

    Mycobacterium tuberculosis stains acid-fast due to its waxy mycolic acid-rich cell wall rather than staining in a typical Gram reaction.

  4. A bacterium that grows optimally at temperatures between 20°C and 45°C is classified as a:

    Answer: Mesophile

    Mesophiles thrive at moderate temperatures (20–45°C) and include most human pathogens.

  5. Which feature distinguishes Archaea from Bacteria at the molecular level?

    Answer: Ether-linked membrane lipids

    Archaea have ether-linked lipids in their membranes, whereas Bacteria have ester-linked lipids.

  6. The Bergey's Manual of Systematic Bacteriology classifies bacteria primarily based on:

    Answer: Phylogenetic and phenotypic characteristics

    Bergey's Manual uses a combination of genetic (16S rRNA phylogeny) and phenotypic data to classify prokaryotes.

  7. A microbiologist identifies a bacterium as coagulase-positive. This result is most useful in identifying which organism?

    Answer: Staphylococcus aureus

    Coagulase positivity is a key biochemical marker that distinguishes Staphylococcus aureus from other staphylococci.