Phases of growth in Microorganism Culture

Question 1

state the four phases of a growth curve in the correct order

Answer 1

lag, log/exponential, stationary, death

Question 2

describe the lag phase

Answer 2

little/no increase in cell number as cells require time to adjust to conditions and produce appropriate enzymes

Question 3

describe the log/exponential phase

Answer 3

cells grow and multiply @ maximum rate. population double with each division as there are no limiting factors

Question 4

describe the stationary phase

Answer 4

production rate is equal to death rate because toxic metabolites begin to accumulate AND the culture medium becomes depleted and nutrients/O2 start to run out

Question 5

describe the death phase

Answer 5

death rate now exceeds production rate and cells die due to lack of nutrients and the build-up of toxic metabolites

Question 6

what is secondary metabolism

Answer 6

occurs during stationary phase, produces secondary metabolites that are not used for growth

Question 7

give an example of secondary metabolism which provides an advantage to an organism

Answer 7

spores increase an organisms ability to survive in a new location

Question 8

how can inducers be used to control the growth in culture

Answer 8

an inducer triggers the production of a specific enzyme, which then produces a desired metabolite

Question 9

how can inhibitors be used to control the growth in culture

Answer 9

inhibitors can be used to avoid the breakdown of a desired product by affecting the enzyme catalysing the reaction

Question 10

what is the difference between viable and total cell count?

Answer 10

total count = total number of cells in a culture including dead cells. viable count = number of viable (live) cells