Question 1

Which of the following best describes the difference between defined and complex media used for microbial growth?

Accepted Answer

Defined media have a precisely known chemical composition, while complex media contain digests of chemically undefined substances.

Question 2

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

Accepted Answer

Streak plate method, because it separates individual cells to form isolated colonies.

Question 3

Which macronutrient is required by all cells and is a major element in all classes of macromolecules?

Accepted Answer

Carbon

Question 4

A bacterium is found to grow optimally at 37°C and is commonly isolated from the human body. How would you classify this organism?

Accepted Answer

Mesophile

Question 5

Which of the following statements about binary fission is correct?

Accepted Answer

Binary fission results in two genetically identical daughter cells.

Question 6

A culture medium contains a dye that changes color when a specific metabolic reaction occurs. This medium is best described as:

Accepted Answer

Differential

Question 7

Which protein is responsible for forming the ring at the center of a prokaryotic cell during division?

Accepted Answer

FtsZ

Question 8

A bacterial culture is grown in a chemostat. Which parameter controls the growth rate of the culture?

Accepted Answer

Dilution rate

Question 9

Which of the following best explains why direct microscopic counts often yield higher cell numbers than viable plate counts?

Accepted Answer

Microscopic counts include both live and dead cells.

Question 10

A bacterium is classified as a halophile. What does this mean about its growth requirements?

Accepted Answer

It requires high salt (NaCl) concentrations.

Question 11

Which enzyme is responsible for breaking down hydrogen peroxide, a toxic byproduct of oxygen metabolism, in aerobic bacteria?

Accepted Answer

Catalase

Question 12

A sample is diluted 1:10 six times, and 1 mL of the final dilution is plated. If 159 colonies are counted, what is the original concentration of cells per mL?

Accepted Answer

$$1.59 	imes 10^5$

Question 13

Which of the following is NOT a limitation of direct microscopic cell counting?

Accepted Answer

It is highly selective for specific species

Question 14

Which of the following best describes the effect of temperature on microbial growth?

Accepted Answer

There is a minimum, optimum, and maximum temperature for growth.

Question 15

Which adaptation is commonly found in psychrophilic (cold-loving) microorganisms?

Accepted Answer

Enzymes with more α-helices and fewer β-sheets

Question 16

Which of the following statements about autoclaving is correct?

Accepted Answer

It uses steam under pressure to achieve temperatures above 100°C.

Question 17

A microbiologist is testing the effectiveness of a new antibiotic using a disc diffusion assay. What does a large zone of inhibition around the disc indicate?

Accepted Answer

The bacteria are susceptible to the antibiotic.

Question 18

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

Accepted Answer

Sterilization removes all microorganisms, while disinfection removes only pathogens.

Question 19

Which of the following is a reason why the 'great plate anomaly' occurs when comparing direct microscopic counts to viable plate counts in natural samples?

Accepted Answer

Microscopic methods count dead cells, while viable methods do not.

Question 20

Which of the following is a function of HEPA filters in biological safety cabinets?

Accepted Answer

They remove airborne microorganisms from the air.

Microbial Growth and Its Control: Structured Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards