Question 1

Which of the following best explains why colony morphology is only used as the first step in microbial identification?

Accepted Answer

Microbes can modify their colony morphology in response to environmental conditions, so further phenotypic or genetic analysis is needed.

Question 2

A student isolates a bacterial colony from a kitchen counter. The colony is circular, convex, has a smooth surface, is opaque, and yellow in color. Which characteristic is most likely to change if the nutrient composition of the agar plate is altered?

Accepted Answer

Color

Question 3

If a single bacterial cell divides repeatedly to form a visible mass, what is the term for this structure?

Accepted Answer

Bacterial colony

Question 4

Which of the following best describes the margin of a bacterial colony?

Accepted Answer

The outer edge of growth

Question 5

A student observes a plate where multiple bacterial colonies have merged to form a single mat of growth. What is this phenomenon called?

Accepted Answer

Bacterial lawn

Question 6

Which of the following statements about contamination in microbiology labs is correct?

Accepted Answer

Microbes residing on humans are a major source of contamination.

Question 7

A colony is described as rhizoid. Which feature distinguishes it from filamentous colonies?

Accepted Answer

Rhizoid colonies have a branching structure.

Question 8

Which of the following is NOT a typical characteristic used to describe colony morphology?

Accepted Answer

Genetic sequence

Question 9

A student samples two locations in their home and cultures bacteria on nutrient agar plates. If the number of colonies on plate A is 50 and on plate B is 200, what is the ratio of colony-forming units (CFUs) between plate B and plate A?

Accepted Answer

$$ \frac{200}{50} = 4 $$

Question 10

Which of the following best describes a 'punctiform' colony?

Accepted Answer

A very small colony distinguished from circular colonies by its size

Question 11

Why is it important to use sterile techniques when handling reagents and equipment in a microbiology lab?

Accepted Answer

To avoid contamination from microbes residing on humans and surfaces

Question 12

A colony is described as 'umbonate.' What does this term refer to?

Accepted Answer

The colony has a central bump called an umbo.

Question 13

Which of the following is a plausible reason why medical professionals use colony morphology as the first step in identifying microbes?

Accepted Answer

Colony morphology allows rapid preliminary identification before more specific tests.

Question 14

A student observes a colony that is moist, sticky, and difficult to remove from the loop. Which term best describes this colony surface?

Accepted Answer

Mucoid

Question 15

If a colony is described as 'translucent,' what does this mean?

Accepted Answer

You can see through the colony, but it is not completely clear.

Question 16

Which step would most likely follow colony morphology in the identification of a microbe in a clinical lab?

Accepted Answer

Sequencing the DNA of the microbe

Question 17

A student is asked to describe the elevation of a colony. Which of the following profiles would be considered 'convex'?

Accepted Answer

A colony with a semi-circular cross section

Question 18

If a colony is described as 'butyrous,' what does this indicate about its surface?

Accepted Answer

The colony has a buttery texture.

Question 19

A student wants to estimate the total number of bacteria in a colony. If each cell divides every 30 minutes and the colony started from a single cell 5 hours ago, how many cells are present? (Assume no cell death and exponential growth.)

Accepted Answer

$$ 2$$^{10}$$ = 1024 $$

Question 20

Which of the following is a limitation of using colony morphology for microbial identification?

Accepted Answer

Colony morphology can be influenced by environmental conditions, leading to misidentification.

Microbial Ubiquity and Colony Morphology: At-Home Microbiology Lab Study Notes

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