unit 6

Question 1

what are the resources microorganisms need to grow

Answer 1

• nutrients
• oxygen ( anaerobic organisms require the absence of oxygen)
• optimum pH
• favorable temperature

Question 2

why do microorganisms should be cultured with great careand what are the safety precautions

Answer 2

• there is a risk that a mutation leads to the formation of a pathogenic strain which could contaminate the bacterial culture
• follow healthy and safety precaution
  . ensure that all equipment are sterilized before culturing bacteria
  . keep culture in the laboratory
  . seal the cultures in a plastic bag and sterilize at a higher temperature and pressure

Question 3

why do microorganisms should be cultured with great careand what are the safety precautions

Answer 3

• there is a risk that a mutation leads to the formation of a pathogenic strain which could contaminate the bacterial culture
• follow healthy and safety precaution
  . ensure that all equipment are sterilized before culturing bacteria
  . keep culture in the laboratory
  . seal the cultures in a plastic bag and sterilize at a higher temperature and pressure

Question 4

what are the steps of culturing

Answer 4

• obtain a supply of the type of microorganism
• ensure that the nutrient medium is kept under sterilize conditions
• by adjusting the medium nutrient conditions will be created for the optimal growth of a microorganism this called selective medium
• microorganisms are introduced to a growth medium using inoculation with a sterilised inoculation loop (can be used to transfer microorganisms)
• incubate at around 20 C

Question 5

what are the methods of measuring the growth of microorganisms

Answer 5

• cell counts
• dilution plating
• measuring area and mass
• optical methods

Question 6

what are the steps of culturing

Answer 6

• obtain a supply of the type of microorganism
• ensure that the nutrient medium is kept under sterilize conditions
• by adjusting the medium nutrient conditions will be created for the optimal growth of a microorganism this called selective medium
• microorganisms are introduced to a growth medium using inoculation with a sterilised inoculation loop (can be used to transfer microorganisms)
• incubate at around 20 C

Question 7

when is it possible to use sampling and what is it used for

Answer 7

for larger and complex habitat where it is not possible to identify and its used for investigating the abundance and distribution of a specie or a population

Question 8

how to measure the growth of microorganisms using cell counts

Answer 8

• microscope and haemocytometer are used to count single-celled microorganisms
• a nutrient broth is diluted with an equal volume of trypan blue which stains dead cells and allows to count only living organisms
• the number of living organisms in four corner square are counted
• the haemocytometer is callibrated to allow the calculations to the number of cells in a known volume of broth

Question 9

how to measure the growth of microorganisms using optical methods

Answer 9

by Turbidimetry which is measuring the intensity of light that passed through the sample
- the greater the number of cells the more turbid the solution is
- this provides an indirect measure of microorganisms
- a calibration curve can be constructed by measuring the turbidity of a series of
control cultures while also using haemocytometer; the results are plotted in a graph of turbidity against cell count