2.10 - Micro-organisms and their applications

Question 1

How fast does bacteria replicate?

Answer 1

Every 20 minutes by binary fission

Question 2

What is binary fission?

Answer 2

Asexual reproduction of bacteria in which they copy their DNA and divide it into 2

Question 3

What are some ways to grow or culture (grow deliberately by humans) bacteria?

Answer 3

Nutrient broth solution

Colonies on an agar plate

Question 4

Nutrient broth solution allows a liquid or gel to provide all the ____ needed for bacteria to grow successfully. These must include ______ for energy, _____ for protein synthesis, plus other minerals

Answer 4

Nutrients
Carbohydrates
Nitrogen

Question 5

Agar plates are created by pouring hot molten agar into sterile ___ ____, which is then allowed to set. Bacteria can be spread onto the plates, and allowed to form individual _____ of the specific bacterium

Answer 5

Petri dishes

Colonies

Question 6

What are pathogens?

Answer 6

Micro-organisms that cause disease

Question 7

What aseptic techniques are used to avoid contamination?

Answer 7

Inculcating loop is sterilised until red hot before and after use
Do not fully remove lid off petri dish as it could allow bacteria in air to contaminate agar (vice versa)
Following inoculation lid of petri dish should be taped down securely
Inoculated agar plates are incubated at 25°C in school laboratories for no more than 24–48 hours. This encourages growth of the culture without growing human pathogens which thrive at body temperature (37°C).
Everything after practical is sterilised

Question 8

The mean division time for bacteria population A is 20 minutes. If the observation begins with one bacterium, calculate how many bacteria will be present after six hours

Answer 8

Bacteria at beginning of growth period X 2^number of divisions

6 hours = 18 X 20 minutes
1 X 2^18 = 262,144

Question 9

How can you slow the rate of bacteria growth?

Answer 9

Reducing the temperature

Question 10

Give an example of when you slow down bacteria growth?

Answer 10

Keeping food in the fridge

Question 11

Give an example of when you can stop bacteria growth?

Answer 11

Keeping food in the freezer. However, the bacteria are not killed, so any increase in temperature would increase bacterial growth.

Question 12

Give an example of when bacteria can be killed?

Answer 12

Cooking food at a very high temperature

Question 13

What are fermenters?

Answer 13

Containers used to grow bacteria and fungi in large amounts

Question 14

Why are fermenters made of metal?

Answer 14

So that it won’t corrode

Question 15

What are the functions and reasons for the below features in fermenters?

1) Steam inlet
2) Nutrient inlet
3) Water jacket with cooling water
4) Air inlet
5) Filter on air inlet
6) Stirring paddles
7) pH probe and intake valve for acid and alkali

Answer 15

1) hot steam sterilises inside to prevent contamination
2) allows nutrients to enter that bacteria needs to grow
3) keeps temp inside constant at the temp that specific bacteria grows at
4) provides Oxygen for aerobic respiration
5) stops micro - organisms getting inside
6) mixes mixture to keep it agitated and temp even
7) pH inside is monitored to check it’s at the optimum value

Question 16

After incubation what happens to the cultured medium?

Answer 16

the culture medium is removed and filtered and the antibiotic (penicillin) extracted. This removes fungal cells, leaving the product penicillin which will need to be treated chemically before use.