Question 1

Which of the following best explains why gram-negative bacteria are generally more resistant to chemical biocides than gram-positive bacteria?

Accepted Answer

Gram-negative bacteria possess an outer membrane that acts as a barrier to many chemicals.

Question 2

A patient is diagnosed with tuberculosis, caused by Mycobacterium tuberculosis. Which staining technique would be most appropriate to identify this organism in a sputum sample?

Accepted Answer

Acid-fast stain

Question 3

Which of the following statements about Pasteur’s experiments is correct?

Accepted Answer

Pasteur demonstrated that microorganisms are present in the air and can contaminate sterile solutions.

Question 4

A microbiologist is using a compound light microscope with an ocular lens of $$10	imes$$ and an objective lens of $$40	imes. $$What is the total magnification?

Accepted Answer

$$400	imes$$

Question 5

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

Accepted Answer

They enable bacteria to survive extreme environmental conditions such as heat and desiccation.

Question 6

A bacterial culture is exposed to a chemical agent that disrupts the plasma membrane. Which of the following is a likely consequence for the bacterial cell?

Accepted Answer

The cell will lose selective permeability, leading to cell death.

Question 7

Which of the following is a correct match between a scientist and their contribution to microbiology?

Accepted Answer

Paul Ehrlich – Proposed the 'magic bullet' concept for selective toxicity.

Question 8

A microbe measures $$10\ \mu m in $$length. How long is this in nanometers ($$nm$$)?

Accepted Answer

$$10,000\ nm$$

Question 9

Which of the following best describes the main difference between prokaryotic and eukaryotic cells?

Accepted Answer

Eukaryotic cells have a nucleus; prokaryotic cells lack a nucleus.

Question 10

A hospital is trying to prevent the spread of a new emerging infectious disease. Which of the following factors is LEAST likely to contribute to the emergence of this disease?

Accepted Answer

Improved sanitation and hygiene

Question 11

Which of the following best explains why food preserved with high concentrations of salt or sugar resists spoilage?

Accepted Answer

High osmotic pressure causes water to leave microbial cells, inhibiting their growth.

Question 12

Which of the following is a beneficial use of bacteria in biotechnology that does NOT involve recombinant DNA technology?

Accepted Answer

Fermentation of milk to produce yogurt

Question 13

A microbiologist is using a phase-contrast microscope to observe living cells. What is the main advantage of this technique over brightfield microscopy?

Accepted Answer

It allows observation of living, unstained cells with enhanced contrast.

Question 14

Which of the following best describes the function of the bacterial glycocalyx (capsule)?

Accepted Answer

It protects bacteria from phagocytosis and helps in adherence to surfaces.

Question 15

A bacterial cell is placed in a hypertonic solution. Which process will occur as a result?

Accepted Answer

Water will leave the cell, causing plasmolysis.

Question 16

Which of the following statements about Koch’s postulates is correct?

Accepted Answer

They are used to prove that a specific microbe causes a specific disease.

Question 17

A laboratory technician is using the streak plate method to isolate bacteria. What is the main purpose of this technique?

Accepted Answer

To obtain pure cultures by separating individual bacterial cells.

Question 18

Which of the following best describes the action of moist heat (such as autoclaving) in microbial control?

Accepted Answer

It denatures proteins and destroys cell membranes.

Question 19

A scientist is using a use-dilution test to evaluate a new disinfectant. What is the main purpose of this test?

Accepted Answer

To assess the effectiveness of a disinfectant against specific microbes on metal or glass surfaces.

Question 20

Which of the following best explains why electron microscopes have greater resolution than light microscopes?

Accepted Answer

Electrons have a much shorter wavelength than visible light.

Microbiology Exam 1 Study Guide: Chapters 1, 3, 4, 6, 7

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