Question 1

Which of the following best describes a colony-forming unit (CFU) in microbiology?

Accepted Answer

A single cell or group of related cells that gives rise to a colony on a culture medium.

Question 2

A hospital lab technician needs to collect a urine specimen for culture. Which method should be used to minimize contamination?

Accepted Answer

Insert a catheter into the bladder using aseptic technique and collect midstream urine.

Question 3

Which type of culture medium contains ingredients with unknown exact chemical composition and is useful when the nutritional needs of an organism are unknown?

Accepted Answer

Complex media

Question 4

A scientist wants to isolate cold-tolerant bacteria from a soil sample. Which enrichment technique should be used?

Accepted Answer

Cold enrichment

Question 5

Which of the following is a differential medium that can distinguish between bacteria based on their ability to lyse red blood cells?

Accepted Answer

Blood agar

Question 6

A researcher is using a chemostat to maintain a bacterial culture in the exponential phase. What is the key feature of a chemostat that allows this?

Accepted Answer

Continuous addition of fresh medium and removal of old medium

Question 7

Which of the following equations correctly represents the calculation of bacterial population after $$n$$ generations, starting from a single cell?

Accepted Answer

$$N = 1 	imes 2^n$$

Question 8

A microbiologist wants to estimate the number of viable bacteria in a sample. Which method involves serial dilution and plating to count colonies?

Accepted Answer

Viable plate count

Question 9

Why is agar commonly used in solid media for culturing microorganisms?

Accepted Answer

It is not metabolized by most microbes and remains solid at incubation temperatures.

Question 10

Which of the following best describes the streak plate method?

Accepted Answer

A technique to isolate pure cultures by spreading microorganisms over the surface of an agar plate.

Question 11

A sample is collected from cerebrospinal fluid for microbiological analysis. What is the recommended collection method?

Accepted Answer

Needle aspiration from subarachnoid space of spinal column

Question 12

Which of the following is an indirect method for estimating microbial growth?

Accepted Answer

Measuring turbidity using a spectrophotometer

Question 13

What is the main advantage of using defined (synthetic) media in microbiology?

Accepted Answer

The exact chemical composition is known, allowing precise control over nutrients.

Question 14

Which preservation method allows storage of microbial cultures for decades?

Accepted Answer

Lyophilization

Question 15

A patient’s wound is suspected to be infected. Which specimen collection method is most appropriate?

Accepted Answer

Sterile swab brushed across the wound surface

Question 16

Which of the following best explains why rapid transport of clinical specimens is important?

Accepted Answer

To prevent contamination and ensure accurate diagnosis

Question 17

Which of the following media is both selective and differential, commonly used to isolate and identify Gram-negative bacteria?

Accepted Answer

MacConkey agar

Question 18

A microbiologist wants to culture a virus. Which technique should be used?

Accepted Answer

Animal or cell culture

Question 19

Which of the following is a direct method for counting microbial cells that does NOT require incubation?

Accepted Answer

Microscopic count using a cell counter

Question 20

A researcher measures the dry weight of a microbial culture to estimate growth. What type of method is this?

Accepted Answer

Indirect method

Microbial Nutrition and Growth: Culturing Microorganisms

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