Q: A culture of E. coli is grown for 80 minutes and undergoes 4 generations of growth. What is the generation time?

$$\text{Generation time} = \frac{80\ \text{minutes}}{4} = 20\ \text{minutes}$$

Question 1

Which of the following best describes the process of binary fission in bacteria?

Accepted Answer

A single cell divides into two genetically identical daughter cells after chromosome replication and septum formation.

Question 2

A hospital patient develops a persistent infection associated with a catheter. Which microbial growth phenomenon is most likely responsible for the difficulty in treating this infection?

Accepted Answer

Biofilm formation on the catheter surface

Question 3

A culture of E. coli is grown for 80 minutes and undergoes 4 generations of growth. What is the generation time?

Accepted Answer

$$	ext{Generation time} = \frac{80\ 	ext{minutes}}{4} = 20\ 	ext{minutes}$$

Question 4

During which phase of the bacterial growth curve does the number of cells dividing equal the number of cells dying?

Accepted Answer

Stationary phase

Question 5

Which of the following best describes a mesophile?

Accepted Answer

An organism that grows best at temperatures between 10–50$$^\circC$$, including human body temperature.

Question 6

Which of the following statements about halophiles is correct?

Accepted Answer

Halophiles thrive in environments with up to 35% salt concentration.

Question 7

A bacterium that can grow in the presence or absence of oxygen and can switch between aerobic respiration and fermentation is classified as:

Accepted Answer

Facultative anaerobe

Question 8

Which enzyme is responsible for converting superoxide ions to hydrogen peroxide in aerobic bacteria?

Accepted Answer

Superoxide dismutase

Question 9

Which of the following media would be most appropriate for isolating a fastidious organism from a clinical sample?

Accepted Answer

Complex (enriched) media

Question 10

A microbiologist wants to distinguish between bacteria that can ferment lactose and those that cannot. Which type of media should be used?

Accepted Answer

Differential media

Question 11

Which physical method is most effective for sterilizing heat-sensitive medical equipment?

Accepted Answer

Filtration

Question 12

Which of the following statements about autoclaving is correct?

Accepted Answer

It uses steam heat at 121$$^\circC $$and 15 psi pressure to achieve sterilization.

Question 13

Which chemical agent is classified as a high-level germicide and is used to sterilize surgical instruments?

Accepted Answer

Aldehydes (e.g., glutaraldehyde)

Question 14

Which of the following best describes a chemoheterotroph?

Accepted Answer

An organism that obtains both energy and carbon from organic compounds.

Question 15

A sample is collected from a wound suspected to contain anaerobic bacteria. Which of the following is the best practice for transporting this sample to the laboratory?

Accepted Answer

Seal the sample in specialized anaerobic transport media tubes immediately after collection.

Question 16

Which of the following is the best definition of sterilization?

Accepted Answer

The process of destroying all living organisms and viruses, including endospores.

Question 17

Which of the following statements about prion control is correct?

Accepted Answer

Prions require a combination of chemical treatments and increased temperature and pressure during autoclaving for elimination.

Question 18

Which of the following best describes the action of a bacteriostatic agent?

Accepted Answer

It inhibits the growth of bacteria without necessarily killing them.

Question 19

A microbiologist uses a spectrophotometer to measure the turbidity of a bacterial culture. What type of cell enumeration method is this?

Accepted Answer

Indirect method

Question 20

Which of the following is a real-world application of differential media in clinical microbiology?

Accepted Answer

Blood agar is used to distinguish between bacteria based on their hemolytic properties.

Fundamentals of Microbial Growth and Decontamination

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