Question 1

Which of the following best describes the effect of temperature on microbial growth, as shown in the first image (growth curve)?

Accepted Answer

Microbial growth rate increases with temperature up to an optimum, then rapidly decreases as temperature exceeds the optimum.

Question 2

The red-pigmented colonies growing on snow in the second image are most likely produced by which group of microbes?

Accepted Answer

Psychrophiles

Question 3

In the third image, which test tube (a-d) represents the growth pattern of an obligate anaerobe in thioglycolate medium?

Accepted Answer

Tube (b)

Question 4

Based on the table in the fourth image, which type of bacteria would you expect to grow only at the bottom of a tube of solid growth medium?

Accepted Answer

Obligate anaerobes

Question 5

Which of the following is a characteristic of bacterial colonies that can be observed on an agar plate, as shown in the fifth image?

Accepted Answer

Colony pigmentation

Question 6

Which of the following best describes a chemically defined medium, as shown in the sixth image?

Accepted Answer

A medium in which the exact chemical composition is known

Question 7

Which component in the complex medium shown in the seventh image provides a source of partially digested protein?

Accepted Answer

Peptone

Question 8

The image of blood agar with clear, greenish, and unchanged areas demonstrates which type of media property?

Accepted Answer

Differential

Question 9

In the image showing MacConkey agar, which organism is most likely to produce pink colonies?

Accepted Answer

Escherichia coli

Question 10

Which of the following best explains the use of dilution and plating, as shown in the image with serial dilutions and agar plates?

Accepted Answer

To estimate the number of viable bacteria in a sample

Question 11

The direct microscopic count method, as shown in the image with a counting chamber, is best suited for which of the following?

Accepted Answer

Counting both live and dead cells

Question 12

Which of the following is a limitation of using an autoclave for sterilization, as shown in the image of the autoclave?

Accepted Answer

It cannot be used for heat-labile materials.

Question 13

Which of the following best describes the action of HEPA filters, as shown in the image of the biological safety cabinet?

Accepted Answer

They physically remove microbes from air.

Question 14

Which pore size filter would you use to remove most bacteria from a solution, according to the membrane filter table?

Accepted Answer

$$0.45\ \mu m$$

Question 15

Which phase of bacterial growth is characterized by a balance between cell division and cell death, as shown in the growth curve image?

Accepted Answer

Stationary phase

Question 16

A sample is measured for turbidity using a spectrophotometer, as shown in the image. What does a lower percent light transmitted indicate?

Accepted Answer

A higher bacterial concentration

Question 17

Which of the following is a direct method for measuring microbial growth?

Accepted Answer

Plate count

Question 18

Which of the following best describes the effect of osmotic pressure on microbial growth?

Accepted Answer

High osmotic pressure inhibits microbial growth by causing plasmolysis.

Question 19

Which of the following is true regarding the use of ionizing radiation for microbial control, as shown in the image of irradiated strawberries?

Accepted Answer

It sterilizes by breaking microbial DNA.

Question 20

Which of the following is a correct equation for the breakdown of hydrogen peroxide by catalase?

Accepted Answer

$$2H_2O_2 \rightarrow 2H_2O + O_2$

Microbial Growth and Control: Study Notes for College Microbiology

Study Guide - Practice Questions