Question 1

Which of the following statements best explains why Archaea are classified separately from Bacteria, despite both being prokaryotic?

Accepted Answer

Archaea possess unique membrane lipids and distinct ribosomal RNA sequences, as shown by Carl Woese's phylogenetic analysis.

Question 2

A patient presents with a persistent lung infection. Laboratory analysis reveals the causative agent is acid-fast. Which cell wall component is most responsible for this staining property?

Accepted Answer

Mycolic acid

Question 3

Which of the following best describes the main difference between Gram-positive and Gram-negative bacterial cell walls?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer and teichoic acids, while Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing lipopolysaccharide.

Question 4

During the Gram-staining procedure, what is the primary reason Gram-negative bacteria appear pink after the final step?

Accepted Answer

The alcohol decolorizer dissolves the outer membrane and allows the safranin counterstain to color the cells.

Question 5

Which of the following is NOT evidence supporting the theory of endosymbiosis for the origin of mitochondria and chloroplasts?

Accepted Answer

Both organelles are surrounded by peptidoglycan cell walls.

Question 6

A microbiologist is trying to identify an unknown bacterium. Which of the following would be the most useful initial step to distinguish between a prokaryote and a eukaryote?

Accepted Answer

Observation of the presence or absence of a nucleus using a light microscope.

Question 7

Which of the following best describes the function of bacterial endospores?

Accepted Answer

They allow bacteria to survive harsh environmental conditions by entering a dormant state.

Question 8

A hospital-acquired infection is traced to a biofilm on a catheter. Which property of biofilms most contributes to their medical significance?

Accepted Answer

Cells in biofilms are more resistant to antibiotics due to the extracellular matrix and altered gene expression.

Question 9

Which of the following statements about the swan-necked flask experiment by Louis Pasteur is correct?

Accepted Answer

It provided evidence for biogenesis by showing that sterilized broth remained free of microbes unless exposed to air-borne contaminants.

Question 10

Which of the following best describes the difference between taxonomy and phylogenetics?

Accepted Answer

Taxonomy involves naming and classifying organisms, while phylogenetics focuses on their evolutionary relationships using genetic data.

Question 11

A bacterial culture is incubated at various temperatures. Growth is observed at $$4^\circ C$$, $$20^\circ C$$, and $$37^\circ C$$, but not at $$55^\circ C. $$Which category best describes this organism?

Accepted Answer

Psychrotroph

Question 12

Which of the following is a key difference between light microscopy and transmission electron microscopy (TEM)?

Accepted Answer

TEM provides much higher resolution and can reveal internal cell structures, while light microscopy is limited by the wavelength of visible light.

Question 13

A Gram-negative bacterium is exposed to penicillin. Which structural feature makes it less susceptible to this antibiotic compared to Gram-positive bacteria?

Accepted Answer

Presence of an outer membrane that restricts entry of penicillin

Question 14

Which of the following best describes the function of bacterial ribosomes?

Accepted Answer

They are involved in protein synthesis by translating mRNA into polypeptides.

Question 15

A microbiologist is using a differential medium to distinguish between two bacterial species based on their ability to ferment lactose. Which type of test is being performed?

Accepted Answer

Biochemical test

Question 16

Which of the following statements about viruses is correct?

Accepted Answer

Viruses are not considered living organisms because they cannot carry out metabolism independently.

Question 17

A facultative anaerobe is grown in a test tube of thioglycollate broth. Where would you expect to see the most growth?

Accepted Answer

Evenly throughout the tube, but with more growth at the top where oxygen is present.

Question 18

Which of the following best explains why Mycoplasma species are resistant to antibiotics that target cell wall synthesis?

Accepted Answer

They lack a cell wall entirely.

Question 19

Which of the following is a correct application of binomial nomenclature in naming microorganisms?

Accepted Answer

The genus name is capitalized and the species name is lowercase, both italicized, e.g., $$	extit{Escherichia coli}.$$

Question 20

A patient is infected with a microbe that is part of the normal microbiota but causes disease after antibiotic treatment. Which term best describes this organism?

Accepted Answer

Opportunistic pathogen

Biology 152: Microbiology Exam 1 Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards