2.6 environmental control of metabolism

Question 1

What are microorganisms?

Answer 1

• archaea
• bacteria
• some species of eukaryotes

Question 2

Why are microorganisms used ?

Answer 2

• their adaptability
• ease of cultivation
• speed of growth

Question 3

What do microorganisms use and produce?

Answer 3

a wide variety of substrates for metabolism and produce a range of products from their metabolic pathways

Question 4

What do many microorganisms produce and some do not? What do the ones that don’t require?

Answer 4

• all the complex molecules required for biosynthesis (amino acids, vitamins, fatty acids)
• they require these to be supplied in the growth media

Question 5

What is required in the growth media when culturing microorganisms?

Answer 5

• their growth media requires raw materials for biosynthesis

- an energy source

Question 6

Where is an energy source derived from?

Answer 6

• chemical substrates

- or from light in photosynthetic microorganisms

Question 7

What are 4 different culture conditions?

Answer 7

• sterility
• control of temperature
• oxygen levels
• pH

Question 8

What do sterile conditions in fermenters do?

Answer 8

• reduce competition with desired microorganisms for nutrients
• and reduce risk of spoilage of the product

Question 9

What are the 4 phases of growth and changes in culture conditions?

Answer 9

• lag phase
• log/exponential phase
• stationary phase
• death phase

Question 10

What happens in the lag phase?

Answer 10

enzymes are induced to metabolise substrates

Question 11

what happens in the log/exponential phase?

Answer 11

the most rapid growth of microorganisms due to plentiful nutrients

Question 12

What happens in the stationary phase?

Answer 12

• the nutrients in the culture are becoming depleted
• production of toxic metabolites
• secondary metabolites such as antibiotics are also produces
• happens when the rate of production of new cells is equal to the death rate of older cells

Question 13

What is the advantage of the secondary metabolites produced in the stationary phase?

Answer 13

in the wild these metabolites confer an ecological advantage by allowing the microorganisms which produce them to outcompete other microorganisms

Question 14

What happens in the death phase?

Answer 14

occurs due to the toxic accumulation of metabolites or the lack of nutrients in the culture
-the death rate of cells is greater then the production rate of new cells

Question 15

What is the difference between viable and total cell count?

Answer 15

• viable cell count includes counting only the living microorganisms
• total cell count involves counting viable and dead cells

Question 16

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

Answer 16

only viable cell count shows a death phase where cell numbers are decreasing

Question 17

What are industrial fermenters used for?

Answer 17

used to culture micro-organisms on a huge scale

-controlled by automatic computers

Question 18

What shape does the graph of the exponential growth phase of a culture make when plotted on semi log graph paper?

Answer 18

straight line

Question 19

what is biosynthesis?

Answer 19

a multi-step, enzyme catalysed process in living organisms in which substrates are converted into more complex products

Question 20

What is a growth medium?

Answer 20

substance which provides microorganisms with an energy source and raw materials for biosynthesis

Question 21

What is a secondary metabolite?

Answer 21

a substance not associated with growth that is produced during the stationary phase of growth of a culture of microorganisms. An example would be antibiotics

Question 22

What does sterility mean?

Answer 22

not containing contaminated microorganisms

Question 23

name a way to control temperature when culturing microorganisms?

Answer 23

water jackets and thermostat

Question 24

name a way of controlling oxygen levels when culturing microorganisms

Answer 24

air inlets, paddles

Question 25

name a way of controlling pH levels when culturing microorganisms

Answer 25

buffer, addition of acids or alkaline

Question 26

what is a way of making things sterile?

Answer 26

aseptic techniques