culturing microorganisms DEFINITELY IN EXAM

Question 1

describe what happens during the process of binary fission

Answer 1

one bacterial cell splits into two bacterial cells

bacteria multiply by simple cell division

Question 2

how often can bacteria carry out binary fission and what conditions are needed for it?

Answer 2

bacteria can carry out binary fission every 20 minutes as long as they have enough nutrients and the temperature is suitable

Question 3

exam question

under ideal conditions a type of bacteria divides every twenty minutes. Calculate the number of bacteria present after 3 hours

Answer 3

number of bacteria= 2 to the power of n
(n= number of rounds of division)

3 hours= 180 minutes

180/20= 9 rounds of division

number of bacteria= 2 to the power of 9
=512
number of bacteria= 5.12 x 10 to the power of 2

Question 4

what 2 places can bacteria be grown in

Answer 4

• nutrient broth solution

- agar gel plate

Question 5

how to avoid contamination of bacteria specimen

Answer 5

• sterilise all petri dishes, bacterial nutrient broth, agar
  (this kills any unwanted microorganisms and prevents contamination)
• sterilise the inoculating loop by passing it through a Bunsen burner flame before using it to transfer bacteria into the culture
• once have transferred bacteria onto the dish attach the lid of the petri dish with adhesive tape.
  (This stops the lid from falling off and unwanted microorganisms entering)
• place the agar plate upside down into an incubator
  (prevents moisture from dripping down onto the bacteria and disrupting colonies)
• in school laboratories bacteria cultures are incubated at 25 degrees Celsius
  (this reduces the chances that harmful bacteria will grow)

Question 6

Which two things must a bacterial cell do before it can divide?

Answer 6

grow

replicate it’s DNA