Unit 2.6 Environmental control of metabolism

Question 1

What are the three types of micro-organisms?

Answer 1

• archaea
• bacteria
• some species of eukaryotes

Question 2

Why are micro-organisms used in the lab?

Answer 2

Because of their
- adaptability
- ease of cultivation
- speed of growth

Question 3

What are the requirements when culturing a micro-organism?

Answer 3

When culturing a micro-organism their growth medium requires raw materials for biosynthesis (amino acids, vitamins, fatty acids…)
as well as an energy source (sugar)

Question 4

What can be an energy source for a micro-organism?

Answer 4

An energy source can be derived either from a chemical substrate or light in photosynthetic micro-organisms

Question 5

What culture conditions must be kept controlled in the culture of micro-organisms?

Answer 5

• conditions must be sterile
• control of oxygen levels
• pH levels

Question 6

What are the phases of micro-organism growth?

Answer 6

• Lag phase
• Exponential/log growth phase
• stationary phase
• death phase

Question 7

What is meant by the Lag phase?

Answer 7

The lag phase is where enzymes are induced to metabolise substrates

Question 8

What is meant by the exponential growth phase?

Answer 8

The exponential growth phase involves the most rapid growth of micro-organisms due to plentiful nutrients

Question 9

What is meant by the stationary phase?

Answer 9

The stationary phase occurs due to the nutrients in the culture medium depleting, and due to the production of toxic metabolites.
During the stationary phase secondary metabolites are also produced. The number of organisms stagnates at this stage

Question 10

What is the purpose of an micro-organism producing secondary metabolites (during the stationary phase)?

Answer 10

The secondary metabolites can be anti-biotics, they confer an ecological advantage by allowing the micro-organism that produces the secondary metabolite to outcompete other micro-organisms

Question 11

What is meant by a viable count?

Answer 11

Viable cell counts involve only counting the living micro-organisms

Question 12

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

Answer 12

In a viable count only the living micro-organisms will be counted however in a total count both the living and the dead cells will be counted.

However the only count that will show that a death phase has happened will be a viable count

Question 13

What is meant by the death phase?

Answer 13

the death phase occurs due to a toxic accumulation of metabolites or lack of nutrients in the culture