Question 1

Which of the following best describes a defined (synthetic) medium used for bacterial growth?

Accepted Answer

A medium in which the exact chemical composition and concentration of every ingredient is known, including all trace elements.

Question 2

Why is defined media rarely used in most microbiology laboratories?

Accepted Answer

It is almost impossible to know all the ingredients and their concentrations, including trace minerals, required for most microbes.

Question 3

Photoautotrophic bacteria can be grown on defined media because:

Accepted Answer

They require only carbon dioxide and light, and possibly trace minerals, for growth.

Question 4

Which of the following is a correct statement about complex media?

Accepted Answer

Most of the ingredients are known, but not all, and it is commonly used in labs.

Question 5

Tryptic Soy Agar (TSA) is an example of complex media. If soybeans from different farms are used to make TSA, what is the likely outcome?

Accepted Answer

The media will still work to grow bacteria, despite minor differences in ingredient levels.

Question 6

Blood agar is an example of which type(s) of media?

Accepted Answer

Enriched and differential media

Question 7

On a blood agar plate, which type of hemolysis is indicated by a clear, glass-like zone around bacterial colonies?

Accepted Answer

Beta ($\beta$) hemolysis

Question 8

Which of the following best explains why Mannitol Salt Agar (MSA) is considered both selective and differential?

Accepted Answer

It contains high salt to select for Staphylococcus species and a pH indicator to differentiate between Staphylococcus aureus and Staphylococcus epidermidis.

Question 9

A patient sample is streaked on MSA. Colonies appear bright yellow. What is the most likely identity of the bacterium?

Accepted Answer

Staphylococcus aureus

Question 10

Which of the following best describes the environmental conditions required to grow Clostridia in the laboratory?

Accepted Answer

An anaerobic environment, such as an anaerobic glove box or jar

Question 11

Streptococci are best grown in which type of environment?

Accepted Answer

Microaerophilic and capneic (high CO$_2$, low O$_2$)

Question 12

Which laboratory method can be used to create a microaerophilic and capneic environment for growing Streptococci?

Accepted Answer

A candle jar

Question 13

Obligate intracellular parasites, such as Rickettsia or viruses, require which of the following for laboratory growth?

Accepted Answer

Living cells, such as tissue culture, eggs, or animals

Question 14

Which of the following statements about Mycobacterium leprae is correct?

Accepted Answer

It cannot be grown on laboratory media and must be grown in armadillos.

Question 15

Sabouraud Dextrose Agar is specifically designed to grow which type of microorganism, and why?

Accepted Answer

Fungal molds, because it is acidic and has high sugar content.

Question 16

Enriched culturing is best described as:

Accepted Answer

A process that increases the numbers of a desired bacterium above others in a mixed sample.

Question 17

In the process of enriching for oil-degrading bacteria from a land sample, why can't these bacteria be used directly for an oil spill in the ocean?

Accepted Answer

Because the ocean has different environmental conditions, such as higher pH and salt, and bacteria must be matched to their native environment.

Question 18

Cold enrichment is used to detect Vibrio cholerae in stool samples because:

Accepted Answer

V. cholerae can replicate at low temperatures, while most other bacteria cannot.

Question 19

Which of the following equations best represents the exponential growth of E. coli under optimal conditions, where $N_0$ is the initial number of cells, $n$ is the number of generations, and $N$ is the final number of cells?

Accepted Answer

$N = N_0 	imes 2^n$

Culturing Bacteria: Media Types, Environmental Requirements, and Identification Methods

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