Question 1

Which of the following best describes the difference between defined and complex media used for culturing microorganisms?

Accepted Answer

Defined media have a known chemical composition, while complex media contain digests of natural products with unknown exact composition.

Question 2

A microbiologist wants to count the number of viable bacteria in a water sample. Which method should she use and why?

Accepted Answer

Viable plate count, because it counts only living, reproducing cells as colony-forming units.

Question 3

Which equation correctly relates the number of cells after a period of exponential growth to the initial cell number and number of generations?

Accepted Answer

$$N_t = N_0$ 	imes 2^n$$

Question 4

A batch culture of E. coli is grown in a closed system. After several hours, the cell number plateaus even though the cells are still alive. What phase is this and what is the main reason for it?

Accepted Answer

Stationary phase; growth is limited by nutrient depletion or waste accumulation.

Question 5

Which adaptation would you expect to find in the cytoplasmic membrane of a psychrophilic bacterium?

Accepted Answer

High content of unsaturated and short-chain fatty acids.

Question 6

A researcher is using a chemostat to grow bacteria. Which parameter can she control independently to affect the specific growth rate?

Accepted Answer

Dilution rate ($$D = F/V)$$

Question 7

Which of the following best explains why 'the great plate count anomaly' occurs when comparing direct microscopic counts to viable plate counts in environmental samples?

Accepted Answer

Many organisms have unique growth requirements and do not grow on standard laboratory media.

Question 8

Which of the following is a correct statement about the effect of temperature on microbial growth?

Accepted Answer

At temperatures above the maximum, protein denaturation and membrane collapse occur.

Question 9

A bacterium isolated from a soda lake grows optimally at pH 10. Which term best describes this organism?

Accepted Answer

Alkaliphile

Question 10

Which of the following is a function of compatible solutes in halophilic microorganisms?

Accepted Answer

They maintain positive water balance by preventing water loss in high-salt environments.

Question 11

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

Accepted Answer

Catalase

Question 12

A microbiologist is testing a new antimicrobial agent. She observes that the agent causes a decrease in cell number and an increase in cell debris. Which type of agent is this most likely to be?

Accepted Answer

Bacteriolytic

Question 13

Which of the following statements about autoclaving is correct?

Accepted Answer

Autoclaving uses steam under pressure to reach 121°C, which kills endospores.

Question 14

Which of the following best describes the action of ultraviolet (UV) radiation as a physical control method?

Accepted Answer

It damages DNA, making it useful for decontaminating surfaces.

Question 15

A facultative anaerobe is inoculated into thioglycolate broth. Where would you expect to see growth?

Accepted Answer

Throughout the tube, but more at the top.

Question 16

Which of the following equations correctly expresses the dilution rate ($$D) in a $$chemostat?

Accepted Answer

$$D = F/V$$

Question 17

Which of the following is a real-world example of a biofilm causing problems in an industrial setting?

Accepted Answer

Biofilms fouling and corroding water pipes.

Question 18

Which of the following best explains why endospores are more resistant to heat sterilization than vegetative cells?

Accepted Answer

Endospores contain dipicolinic acid and are metabolically dormant.

Question 19

A sample contains $$1 	imes 10^7$ cells/mL. After three generations, how many cells/mL will there be, assuming no cell death?

Accepted Answer

$$8 	imes 10^7$

Question 20

Which of the following is NOT a correct pairing of microorganism and its environmental adaptation?

Accepted Answer

Psychrophile – high temperature

4: Microbial Growth and Its Control – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards