U2.6 Environmental control of metabolism

Question 1

Where can microorganisms come from?

Answer 1

The three domains of life- archaea, bacteria and some species of eukaryote.

Question 2

What do microorganisms do?

Answer 2

Metabolise a wide variety of substrates allowing them to survive in a wide range of ecological niches.

Question 3

What are the benefits of microorganisms?

Answer 3

They are adaptable, they can be easily cultivated, they have fast rates of growth, they produce a wide range of products from their metabolic pathways which can be used for human benefit.

Question 4

What does microorganism growth media contain?

Answer 4

Raw materials for biosynthesis and an energy source.

Question 5

What can some microorganisms produce?

Answer 5

Their required complex molecules for biosynthesis

Question 6

What complex molecules are needed for biosynthesis?

Answer 6

Amino acids, vitamins and fatty acids.

Question 7

What is a growth medium?

Answer 7

Can be either solid or liquid, provides the surface where micro-organisms grow.

Question 8

How is an energy source for a microorganism derived?

Answer 8

From a chemical substrate, or from light in photosynthetic microorganisms.

Question 9

What is a fermenter used to do in the culture of microorganisms?

Answer 9

Provide optimum conditions for microorganisms.

Question 10

State three examples of products in fermenters.

Answer 10

Antibiotics, enzymes, vaccines.

Question 11

What is culturing?

Answer 11

Culturing is a process that results in the multiplying of micro-organisms under laboratory conditions.

Question 12

What conditions must be controlled when culturing?

Answer 12

Temperature
O2 levels
pH - by adding acid or alkali or using a buffer solution
Nutrients - within the growth media
Sterility - to stop any contamination from other micro-organisms.

Question 13

How might contamination be prevented?

Answer 13

Heat sterilisation by using an autoclave to kill microbes under high temperatures.
Radiation sterilisation by using electromagnetic radiation like UV waves.
Using chemicals like disinfectants and antiseptics.

Question 14

Why do conditions need to be sterile in fermenters?

Answer 14

To reduce competition with the desired micro-organisms for nutrients and reduce the risk of spoilage of the product.

Question 15

What are the four phases of growth and changes in culture conditions?

Answer 15

Lag, Log/exponential, Stationary, Death

Question 16

Describe the lag phase.

Answer 16

Enzymes are just beginning to be induced to metabolise substrates, so growth is slow.

Question 17

Describe the log/exponential phase.

Answer 17

Rapid growth of microorganisms due to plentiful nutrients.

Question 18

Describe the stationary phase.

Answer 18

Due to nutrient depletion and toxic metabolites, graph is stationary.

Question 19

Describe the death phase.

Answer 19

Due to toxic metabolite accumulation and lack of nutrients, there is a decrease in viable cells.

Question 20

What is meant by viable cell count?

Answer 20

Only takes into account LIVING cells.

Question 21

What is meant by total cell count?

Answer 21

Takes into account all cells, living and dead.

Question 22

How do we see a decrease in the graph at the death phase?

Answer 22

Only viable cell count shows a death phase