Microbial Media and Measurement EXAM 2

Question 1

What is culture media used for?

Answer 1

To grow, transport, and store microorganisms.

Question 2

What must culture media contain?

Answer 2

All the nutrients the organism requires for growth.

Question 3

What are the different ways media is classified?

Answer 3

1. Chemical constituents.
2. Physical nature.
3. Function.

Question 4

What are the two sub-categories of chemical constituents?

Answer 4

1. Defined/synthetic.
2. Complex.

Question 5

What is defined/synthetic media?

Answer 5

Media where each ingredient can be defined with a chemical formula.
*Useful for picky bacteria or trying to replicate specific conditions.

Question 6

What is complex media?

Answer 6

Media that contains some ingredients of unknown chemical composition.
*Useful for growing most kinds of bacteria.

Question 7

What are some common media components?

Answer 7

1. Peptones.
2. Extracts.
3. Agar.

Question 8

What are peptones?

Answer 8

Protein hydrolysates from protein sources.

Question 9

What are extracts?

Answer 9

Aqueous extracts, usually from beef or yeast.

Question 10

What is agar?

Answer 10

Sulfated polysaccharide solidifying agent.
*Most microorganisms cannot degrade it.

Question 11

What are the three physical natures of media?

Answer 11

1. Solid.
2. Semi-solid.
3. Liquid.

Question 12

What are the 4 potential functions of media?

Answer 12

1. Supportive/general purpose.
2. Enriched.
3. Selective.
4. Differential.

Question 13

What is supportive/general purpose media used for?

Answer 13

Support the growth of many microorganisms.

Question 14

What is enriched media used for?

Answer 14

To grow bacteria with specific needs.

Question 15

What is selective media used for?

Answer 15

Allowing for the growth of growth of particular microorganisms, while inhibiting the growth of others.

Question 16

What isthe purpose of differential media?

Answer 16

To distinguish among different groups of microbes and even permit tentative identification based on their biological characteristics.

Question 17

How are obligate anaerobes cultured?

Answer 17

In an anoxic chamber or a similar device.

Question 18

What does it mean to isolate from a pure culture?

Answer 18

Taking bacteria that is known to have been grown from a single cell

Question 19

Who came up with the principle of isolating a cell from a pure culture?

Answer 19

Robert Koch.

Question 20

What does isolating a pure culture allow for?

Answer 20

Studying a single microorganism in a mixed culture.

Question 21

What are 3 techniques for isolating pure cultures?

Answer 21

1. Streak plate.
2. Spread plate.
3. Pour plate.

Question 22

What is the streak plate technique?

Answer 22

Spreading a mixture of cells on a agar surface so that individual cells are well separated and can reproduce to form a separate colony.

Question 23

What is the spread plate technique?

Answer 23

A small volume of diluted mixture (25-250 cells) is transferred.

Question 24

How is the diluted mixture spread evenly over the surface of the plate?

Answer 24

With a sterile bent rod.

Question 25

What is the pour plate technique?

Answer 25

A sample is serially diluted then poured onto agar before it solidifies.

Question 26

What are the requirements for a continuous microbial culture in an open system?

Answer 26

1. Continual provision of nutrients. 2. Continual removal of waste. *Cells are maintained in the log phase at a constant biomass for extended periods.

Question 27

What are continuous cultures used to study?

Answer 27

1. Microbial growth at very low nutrient concentrations. 2. Interactions between microbes under conditions resembling an aquatic environment. 3. Food and industrial microbiology.