Bacteria count

Question 1

What is the purpose?

Answer 1

• To see the amount of bacteria present in a sample

Question 2

What equipment is used?

Answer 2

1. 5 Test tubes
2. Test tube rack
3. Beaker
4. Water solution
5. E. coli bacteria
6. Pipette
7. Pen
8. Bunsen burner
9. Heat proof mat

Question 3

What are the safety protocols? (Hazard)

Answer 3

1. Bunsen burner
2. E. coli bacteria
3. Glass test tubes

Question 4

What are the safety protocols? (Risk)

Answer 4

1. You could burn yourself
2. Your hair could set on fire
3. You could get bacteria in your eyes
4. The test tubes could break and could cause an injury

Question 5

What are the safety protocols? (Precaution)

Answer 5

1. Put the flame on the safety flame
2. Tie your hair back
3. Wear safety goggles
4. Ensure that the test tubes are placed in a test tube rack to prevent breakages

Question 6

What is the method? (Dilutions)

Answer 6

1. Get 5 test tubes, test tube rack, beaker
2. Fill a beaker with water solution
3. Fill the test tubes with 9ml of the water solution
4. Label the test tubes: 10-1, 10-2,10-3,10-4,10-5
5. Get the E. coli and pipette 1ml of the E. coli into the 10-1 test tube and mix the solution together
6. Pipette 1ml of the 10-1 solution into the 10-2 solution and mix the solution
7. Pipette 1ml of the 10-2 solution into the 10-3 solution and mix the solution
8. Pipette 1ml of the 10-3 solution into the 10-4 solution and mix the solution
9. Pipette 1ml of the 10-4 solution into the 10-5 solution and mix the solution

Question 7

What is the method? (Plating)

Answer 7

1. Get a Bunsen burner and a heatproof mat
2. Light the Bunsen burner and turn the flame onto the safety flame
3. Get 4 petri dishes
4. Label them with the E. coli bacteria, the date and 10-2, 10-3, 10-4, 20-5
5. Pipette 1ml of the 10-2 solution into the labelled 10-2 petri dish and spread the solution around the petri dish to allow equal coverage
6. Pipette 1ml of the 10-3 solution into the labelled 10-3 petri dish and spread the solution around the petri dish to allow equal coverage
7. Pipette 1ml of the 10-4 solution into the labelled 10-4 petri dish and spread the solution around the petri dish to allow equal coverage
8. Pipette 1ml of the 10-5 solution into the labelled 10-5 petri dish and spread the solution around the petri dish to allow equal coverage
9. After every petri dish has 1ml of the solution seal them with Sellotape to ensure they don’t get contaminated

Question 8

What is the method? (Calculations)

Answer 8

1. Count the colonies which are present on each petri dish
2. Place the numbers into the results table
3. Multiple the concentration (10-?) and the number of colonies there are together
4. This will then give you the number of bacteria which is on the plate CFU/ml