Question 1

Which of the following best describes a biofilm?

Accepted Answer

A mixed microbial community attached to a surface with channels for nutrient and waste exchange.

Question 2

A hospital is experiencing persistent infections with Pseudomonas aeruginosa on catheters, despite regular surface cleaning. Which property of biofilms most likely explains this persistence?

Accepted Answer

Cells deep within the biofilm are protected from disinfectants and are difficult to kill.

Question 3

Which of the following equations correctly represents the number of cells ($$N) $$after $$n$$ generations, starting from a single cell, assuming binary fission?

Accepted Answer

$$N = 2^n$$

Question 4

A culture of E. coli is placed in fresh nutrient broth. After a short period, the cells begin to divide rapidly. Which phase of the bacterial growth curve does this describe?

Accepted Answer

Log (exponential) phase

Question 5

Which of the following best explains why Mycobacterium tuberculosis has a much longer generation time than E. coli?

Accepted Answer

It has a thicker, waxy cell wall that slows nutrient uptake and cell division.

Question 6

A bacterium isolated from a hot spring grows optimally at 70°C. How would you classify this organism?

Accepted Answer

Thermophile

Question 7

Which adaptation allows halophiles to survive in high-salt environments like the Dead Sea?

Accepted Answer

They maintain a high concentration of organic materials and ions in their cytoplasm to avoid plasmolysis.

Question 8

Which of the following best describes an obligate anaerobe?

Accepted Answer

It does not use oxygen and will die in its presence.

Question 9

A microbe that requires several amino acids and vitamins in its growth medium is best described as:

Accepted Answer

Fastidious

Question 10

Which of the following media would be best for isolating a fastidious pathogen from a patient sample?

Accepted Answer

Complex media

Question 11

A sample is streaked onto mannitol salt agar. After incubation, the agar turns bright yellow. What does this indicate?

Accepted Answer

The organism is Gram-positive and can ferment mannitol.

Question 12

Which of the following statements about autoclaving is correct?

Accepted Answer

It applies steam heat and pressure to sterilize most objects within 20 minutes.

Question 13

Which of the following is a limitation of boiling as a method of decontamination?

Accepted Answer

Some endospores can survive hours of boiling.

Question 14

Which of the following disinfectants is classified as a high-level disinfectant and is commonly used to sterilize implant devices such as pacemakers?

Accepted Answer

Ethylene oxide

Question 15

A laboratory technician needs to culture an obligate anaerobe. Which of the following methods would be most appropriate?

Accepted Answer

Incubate the culture in a jar with oxygen-reacting chemicals to create an anaerobic environment.

Question 16

Which of the following best describes the action of halogens as disinfectants?

Accepted Answer

They oxidize cell components, especially proteins and nucleic acids.

Question 17

A patient sample is tested using a flow cytometer. What is being measured?

Accepted Answer

The number of fluorescently labeled cells as they pass through a laser.

Question 18

Which of the following best explains why pasteurization does not sterilize milk?

Accepted Answer

Pasteurization uses temperatures too low to kill all endospores and some non-pathogenic microbes.

Question 19

Which of the following statements about detergents is correct?

Accepted Answer

Detergents are amphipathic and can remove both water-soluble and water-insoluble substances.

Question 20

A microbiologist is using a spectrophotometer to estimate the number of bacteria in a culture. What is being measured?

Accepted Answer

The amount of light absorbed by the culture, which correlates with turbidity.

Microbial Growth and Decontamination: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards