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 Koch’s postulates is correct?

Accepted Answer

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

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 harsh environmental conditions.

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 statement about the difference between prokaryotic and eukaryotic ribosomes?

Accepted Answer

Prokaryotic ribosomes are $$70S$$, while eukaryotic ribosomes are $$80S.$$

Question 8

A microbiologist wants to isolate a pure culture of a bacterium from a mixed sample. Which method should they use?

Accepted Answer

Streak plate method

Question 9

Which of the following best describes the process of group translocation in bacteria?

Accepted Answer

Active transport in which a substance is chemically modified during its passage across the membrane

Question 10

A food company wants to prevent microbial growth in canned foods. Which method is most effective for sterilization?

Accepted Answer

Autoclaving at $$121^\circ \mathrm{C}$$ for 15 minutes

Question 11

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

Accepted Answer

Production of yogurt by fermentation

Question 12

A scientist is using a transmission electron microscope (TEM) to study a bacterial cell. What is the main advantage of using TEM over a compound light microscope?

Accepted Answer

TEM provides higher resolution, allowing visualization of internal cell structures.

Question 13

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

Accepted Answer

It protects the cell from phagocytosis and helps in attachment to surfaces.

Question 14

A bacterial cell is placed in a hypertonic solution. What is the most likely outcome?

Accepted Answer

The cell will lose water and undergo plasmolysis.

Question 15

Which of the following statements about biofilms is correct?

Accepted Answer

Biofilms are communities of microorganisms attached to a surface and embedded in a self-produced matrix.

Question 16

A culture medium contains $$5\ \mathrm{g} of $$NaCl per liter. If a bacterium requires a hypotonic environment for optimal growth, what will likely happen to the bacterium in this medium?

Accepted Answer

The bacterium will undergo plasmolysis due to water loss.

Question 17

Which of the following is a correct statement about the use of phosphate salts as buffers in microbial growth media?

Accepted Answer

Phosphate salts provide essential phosphorus for microbial metabolism in addition to buffering capacity.

Question 18

A laboratory technician is using the disk-diffusion method to test the effectiveness of several disinfectants. What is being measured in this method?

Accepted Answer

The diameter of the zone of inhibition around each disk

Question 19

Which of the following best describes the difference between sterilization and disinfection?

Accepted Answer

Sterilization removes or destroys all forms of microbial life, while disinfection eliminates most pathogens but not necessarily all microbes.

Question 20

A bacterial population increases from $$1 	imes 10^3$ to 1$$ 	imes $$10^9$$ cells in 10 hours. Assuming exponential growth, what is the approximate generation time $$g in $$hours? (Use the formula $$n = \frac{\log N_t - \log N_0$}{\log 2}$$, where $$n is $$the number of generations, $$N_t is $$the final cell number, $$N_0 is $$the initial cell number, and $$g = \frac{t}{n}.)$$

Accepted Answer

About $$0.86$$ hours

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

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