Question 1

Which of the following best explains why Gram-negative bacteria are generally more resistant to disinfectants than Gram-positive bacteria?

Accepted Answer

They possess an outer membrane that limits the entry of many antimicrobial agents.

Question 2

A patient is infected with a bacterium that can survive boiling water for 10 minutes. Which structure is most likely responsible for this resistance?

Accepted Answer

Endospore

Question 3

During which phase of the bacterial growth curve do bacteria grow at their maximum rate, and why is this phase clinically significant?

Accepted Answer

Log (exponential) phase; because bacteria are most susceptible to antibiotics

Question 4

Which of the following best describes the process of active transport in a bacterial cell?

Accepted Answer

Movement of molecules against the concentration gradient, using energy

Question 5

A scientist is using the Ames test to evaluate a new food additive. What is the primary purpose of the Ames test?

Accepted Answer

To assess whether a substance is mutagenic by measuring its ability to cause mutations in bacteria

Question 6

Which of the following is the best evidence supporting the three-domain system of classification?

Accepted Answer

Major differences in the sequence of ribosomal RNA between all three domains

Question 7

A hospital is trying to prevent infections in immunocompromised patients. Which of the following is a practical method to reduce the risk of infection from normal microbiota?

Accepted Answer

Strict hand hygiene and aseptic techniques by healthcare workers

Question 8

Which of the following statements about biofilms is FALSE?

Accepted Answer

Biofilms are more sensitive to antibiotics.

Question 9

A researcher is studying a bacterium that can transfer genetic material to another bacterium through a pilus. What is this process called?

Accepted Answer

Conjugation

Question 10

Which of the following best explains why 70% ethanol is more effective at killing bacteria than 100% ethanol?

Accepted Answer

70% ethanol penetrates cell walls better and denatures proteins more effectively

Question 11

A diabetic patient develops a bloodstream infection from a normally harmless skin bacterium. Which term best describes this type of infection?

Accepted Answer

Opportunistic infection

Question 12

Which of the following is NOT a major nutrient required for microbial growth?

Accepted Answer

Agarose

Question 13

Which of the following best describes the structure of a carbohydrate molecule?

Accepted Answer

Composed of (CH2O) units

Question 14

A nurse is disinfecting a hospital room previously occupied by a patient with Clostridioides difficile. Why might standard disinfectants be ineffective against this bacterium?

Accepted Answer

C. difficile forms endospores that are highly resistant to many disinfectants

Question 15

Which of the following best describes the function of ribosomes in a cell?

Accepted Answer

Synthesis of proteins from mRNA templates

Question 16

Which of the following is a unique property of water that is critical for life?

Accepted Answer

Water has a high heat capacity and is an excellent solvent

Question 17

Which of the following best describes the process of nucleic acid hybridization?

Accepted Answer

Pairing occurs between complementary DNA or RNA strands

Question 18

A scientist is classifying a newly discovered microbe. Which method would provide the most reliable information about its evolutionary relationships?

Accepted Answer

Analyzing ribosomal RNA (rRNA) sequences

Question 19

Which of the following best describes the central dogma of molecular biology?

Accepted Answer

DNA is transcribed into mRNA, which is then translated into protein

Question 20

A patient is given a chemotherapy drug that is mutagenic in the Ames test. Why might this drug still be used to treat cancer?

Accepted Answer

The benefits of killing cancer cells outweigh the risks of mutagenicity

Microbiology Midterm Exam Study Guidance

Study Guide - Practice Questions

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