Q: If a bacterium has a generation time of 30 minutes, how many cells will result from a single cell after 3 hours of exponential growth? Use the formula $$N = N_0$ \times 2^n$$, where $$N_0 is $$the initial cell number and $$n is $$the number of generations.

$$N = 1 \times 2^6$ = 64$$ cells

Q: If a culture of E. coli is started with 100 cells and has a generation time of 20 minutes, how many cells will be present after 2 hours of exponential growth? Use $$N = N_0$ \times 2^n.$$

$$N = 100 \times 2^6$ = 6400$$ cells

Question 1

Which of the following best describes binary fission in bacteria?

Accepted Answer

A process where a single cell divides into two genetically identical daughter cells after chromosome replication and partitioning

Question 2

A hospital patient develops a persistent bloodstream infection due to bacteria growing on a catheter. What microbial feature most likely contributes to the persistence of this infection?

Accepted Answer

Biofilm formation on the catheter surface

Question 3

Which phase of the bacterial growth curve is characterized by rapid genome replication and exponential increase in cell number?

Accepted Answer

Log (exponential) phase

Question 4

If a bacterium has a generation time of 30 minutes, how many cells will result from a single cell after 3 hours of exponential growth? Use the formula $$N = N_0$ 	imes 2^n$$, where $$N_0 is $$the initial cell number and $$n is $$the number of generations.

Accepted Answer

$$N = 1 	imes 2^6$ = 64$$ cells

Question 5

Which statement best explains why biofilms are difficult to treat in clinical settings?

Accepted Answer

Biofilms protect bacteria from antibiotics and immune responses

Question 6

Which of the following microbes would most likely thrive in a compost pile with temperatures around 70°C?

Accepted Answer

Thermophiles

Question 7

A bacterium is isolated from a hot spring with a pH of 2. Which adaptation is most likely present in this organism?

Accepted Answer

Proton pumps that export excess protons to maintain cytoplasmic pH

Question 8

Which oxygen requirement group can switch between aerobic respiration and fermentation depending on environmental oxygen levels?

Accepted Answer

Facultative anaerobes

Question 9

In a chemostat, what is the primary purpose of continuously adding fresh media and removing waste?

Accepted Answer

To maintain the culture at a constant exponential growth rate

Question 10

Which of the following best describes the stationary phase in a closed batch culture?

Accepted Answer

Nutrients are depleted, waste accumulates, and population growth rate levels off

Question 11

A bacterium isolated from the deep sea is able to withstand high pressure. What term best describes this organism?

Accepted Answer

Barophile

Question 12

Which enzyme is responsible for converting hydrogen peroxide ($$H_2O_2) $$into water and oxygen in bacteria?

Accepted Answer

Catalase

Question 13

Which group of bacteria is most commonly associated with human pathogens?

Accepted Answer

Mesophiles

Question 14

A microbe grows best at pH 10. What is the correct classification for this organism?

Accepted Answer

Alkaliphile

Question 15

Which of the following is a common misconception about obligate anaerobes?

Accepted Answer

They do not use oxygen in their metabolism and are killed by reactive oxygen species

Question 16

If a culture of E. coli is started with 100 cells and has a generation time of 20 minutes, how many cells will be present after 2 hours of exponential growth? Use $$N = N_0$ 	imes 2^n.$$

Accepted Answer

$$N = 100 	imes 2^6$ = 6400$$ cells

Question 17

Which adaptation would you expect in a halophile living in a highly saline environment?

Accepted Answer

Accumulation of compatible solutes to combat osmotic stress

Question 18

Which of the following statements about microbial growth in nature versus the laboratory is correct?

Accepted Answer

In the laboratory, microbes are typically grown as pure cultures, while in nature they intermingle with other species

Question 19

Which of the following best describes the death phase of a bacterial growth curve?

Accepted Answer

Cells die at an exponential rate due to waste buildup and nutrient depletion

Question 20

A bacterium is found to lack both catalase and superoxide dismutase. What is the most likely oxygen requirement classification for this organism?

Accepted Answer

Obligate anaerobe

Fundamentals of Microbial Growth and Decontamination: Study Notes CHAPTER 7A

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