Environmental Control of Metabolism 2.6

Question 1

List the three types of micro-organisms.

Answer 1

Micro-organisms are:
 Archaea
 Bacteria
 Some species of Eukaryotes

Question 2

What do micro-organisms use a wide variety of substrates for?

Answer 2

Micro-organisms use a wide variety of substrates for
metabolism and produce a range of products from their
metabolic pathways.

Question 3

Why are micro-organism used?

Answer 3

Micro-organisms are used because of their adaptability,
ease of cultivation and speed of growth.

Question 4

When culturing micro-organisms, what does their growth media require?

Answer 4

When culturing micro-organisms, their growth media require raw materials for
biosynthesis as well as an energy source.

Question 5

What are examples of the complex molecules required for biosynthesis produce by micro-organism?

Answer 5

Many micro-organisms produce all the complex molecules required for biosynthesis, for example amino acids, vitamins and fatty acids. Other micro- organisms require these to be supplied in the growth media.

Question 6

What are the conditions needed to culture micro-organisms?

Answer 6

Culture conditions:
 Sterility
 Control of temperature
 Oxygen levels
 pH

Question 7

Where is an energy source derived from in micro-organism?

Answer 7

An energy source is derived either from chemical
substrates or from light in photosynthetic micro-organisms.

Question 8

What do sterile conditions do in fermenters?

Answer 8

Sterile conditions in fermenters:
 Reduce competition with other micro-organisms for nutrients
Reduce the risk of spoilage of the product.

Question 9

What is the lag phase?

Answer 9

Lag phase is where enzymes are induced to metabolise substrates.

Question 10

What is the log phase?

Answer 10

Log/Exponential phase contains the most rapid growth of micro-organisms due to
plentiful nutrients.

Question 11

What is the stationary phase?

Answer 11

Stationary phase occurs due to the nutrients in the culture media becoming depleted
and the production of toxic metabolites.

Question 12

Why does the death phase occur?

Answer 12

Death phase occurs due to:
 Toxic accumulation of metabolites
 Lack of nutrients in the culture

Question 13

What is also produced in the stationary phase?

Answer 13

Secondary Metabolites are also produced, such as antibiotics.

Question 14

Why are these metabolites useful in the wild?

Answer 14

In the wild these metabolites confer an Ecological Advantage by allowing the micro-
organisms which produce them to outcompete other micro-organisms

Question 15

What is the difference between the viable cell count and the total cell count?

Answer 15

Viable Cell Counts involve counting only the living micro-organisms
Total Cell Counts involve counting viable and dead cells.