2. Methods

2.1

Experiment A:

Items:

Quantity:

Sterilised paper disk	5
Petri dishes	6
Samples of bacteria in canteen	0.3ml in total, 0.05ml / 50 ul for each petri dish
Labels for petri dishes	6 post-its labelled
Mama Lemon	1ml
Clorox	1ml
Dettol	1ml
Jif	1ml
Mr Muscle	1ml
Safety materials (goggles, gloves, masks)	x3 sets
Parafilm	1 strip for each petri dish, 6 strips in total
Agar Jelly	75 ml in total, 12.5 ml for each petri dish
5ml small bottles	5 bottles, each one to be filled with 1ml of each respective soap.
15cm ruler	1
Cotton bud swab	1
Tweezer	1

Experiment B:

Items:

Quantity:

Sterilised paper disk	5
Petri dishes	6
Samples of bacteria in canteen	0.3ml in total, 0.05ml / 50 ul for each petri dish
Labels for petri dishes	6 post-its labelled
Sterilised water	1ml
Clorox	1ml
Test tube	5
Test tube holder	1
Safety materials (goggles, gloves, masks)	x3 sets
Parafilm	1 strip for each petri dish, 6 strips in total
Agar Jelly	75 ml in total, 12.5 ml for each petri dish
5ml small bottles	5 bottles, each one to be filled with 1ml of each respective soap.
15cm ruler	1
Cotton bud swab	1
Tweezer	1

2.2 Diagrams

Experiment A

Figure 1

  figure 2

Figure 3: Experimental setup

Experiment B

Figure 4

Figure 5: Experimental setup 

2.3 Procedures: Detail all procedures and experimental design to be used for data collection

Experiment A

According to Tom Besty, DC and Jim Keogh, RN, (2005), step 6 was adapted from their book,

Microbiology Demystified from chapter 6, page 104 - 105.

According to Wayne, C, (2015), steps 1 - 4, 6 - 13 and 15-18 were adapted from their website,

ISS S205 Group A, Annex A, Group project proposal. 

According to Meredith, J, (2019), step 14 was adapted from their website, Wikihow, How to

grow bacteria in a Petri dish. 

1. Collect sample bacteria from canteen uncle. 
   
   
2. Set up 6 Petri dishes.
   
   
3. 
   

   Light up the alcohol lamp to create an updraft to prevent dust from entering the Petri

   
   

   dishes. 
   
   
4. Put 12.5 ml of agar jelly into each petri dish.
   
   
5. 
   

   Use a cotton bud swab to spread 50ul of sample bacteria evenly from school canteen into

   
   

   each of the Petri dishes. Only put on safety goggles at this point to prevent bacteria from

   getting into the eye.  
   
   
6. Leave 17.45ml as bacteria need carbon dioxide and oxygen to live. 
   
   
7. 
   

   Use a tweezer and soak each sterilised filter paper disk into each solution (Mama lemon,

   
   

   Clorox, Dettol,  Jif and Mr Muscle)
   
   
8. Soak a total of 5 sterilised filter paper disks of different solutions. 
   
   
9. Place 1 different soaked sterilised filter paper disk into each petri dish. 
   
   
10. Do not place any sterilised filter paper disk for the last one as it is the control variable. 
    
    
11. 
    

    Sterilize the tweezer after placing a soaked sterilised filter paper disk by putting above the

    
    

    alcohol lamp to prevent the different soaps from mixing. 
    
    
12. Name all the different Petri dishes with a sticker to label. 
    
    
13. 
    

    Mask all the Petri dishes with a parafilm tape and place all the Petri dishes upside down

    
    

    into the incubator for 4 days at 30 to 40 degrees celsius
    
    
14. 
    

    Check and measure all the petri dishes sterilised filter paper disk diameter of the inhibition

    of bacterial growth (the diameter of the bacteria killed) with the 15 cm ruler every day and
    

    enter the data into the google sheet. Afterwards, we draw out a histogram. 
    
    
15. 
    

    Take out the petri dishes every 4 days to record the findings and take photos with a ruler

    
    

    and a label
    
    
16. Repeat steps 1 - 16 if the experiment goes wrong
    
    
17. Redo experiment after a successful experiment
    
    

Experiment B

1. Collect sample bacteria from canteen uncle.
   
   
2. Set up 5 Petri dishes.
   
   
3. 
   

   Light up the alcohol lamp to create an updraft to prevent dust from entering the Petri

   
   

   dishes. 
   
   
4. Put 12.5 ml of agar jelly into each petri dish.
   
   
5. 
   

   Use a cotton bud swab to spread 50ul of sample bacteria evenly from school canteen into

   
   

   each of the Petri dishes. Only put on safety goggles at this point to prevent bacteria from

   getting into the eye.  
   
   
6. 
   

   Put 5 different concentrations of Clorox into their respective test tubes

   
   

   (8ml of water and 2ml of Clorox, 6ml of water and 4ml of Clorox, 4ml of water and 6ml of

   Clorox, 2ml of water and 8ml of Clorox, and undiluted Clorox)   
   
   
7. Leave 17.45ml as bacteria need carbon dioxide and oxygen to live. 
   
   
8. Use a tweezer and soak each sterilised filter paper disk into each solution.  
   
   
9. Soak a total of 5 sterilised filter paper disks of different solutions. 
   
   
10. Place 1 different soaked sterilised filter paper disk into each petri dish. 
    
    
11. Do not place any sterilised filter paper disk for the last one as it is the control variable. 
    
    
12. 
    

    Sterilize the tweezer after placing a soaked sterilised filter paper disk by putting it above

    
    

    the alcohol lamp to prevent the different soaps from mixing. 
    
    
13. Name all the different Petri dishes with a sticker to label. 
    
    
14. 
    

    Mask all the Petri dishes with a parafilm tape and place all the Petri dishes upside down

    
    

    into the incubator for 4 days at 30 to 40 degrees celsius
    
    
15. 
    

    Check and measure all the petri dishes sterilised filter paper disk diameter of the inhibition

    of bacterial growth (the diameter of the bacteria killed) with the 15 cm ruler every day and
    

    enter the data into the google sheet. Afterwards, we draw out a histogram. 
    
    
16. 
    

    Take out the petri dishes every 4 days to record the findings and take photos with a ruler

    
    

    and a label
    
    
17. Repeat steps 1 - 16 if the experiment goes wrong.   
    
    
18. Redo experiment after a successful experiment
    
    

2.4 Data Analysis: Describe the procedures you will use to analyze the data / results. 

1. 
   

   Determine the diameter of the inhibition of bacteria by taking a picture of a 15cm ruler on

   
   

   the petri dish with black background behind the petri dish and take photos
   
   
2. calculate the area of the inhibition zone from photos making sure it is to scale
   
   
3. Plot a histogram of the area of the inhibition zone to the type of cleaning agent.
   
   
4. Plot a graph of inhibition zone against concentration of cleaning agent. 
   
   

2.5 Data Analysis

1. 
   

   Determine the diameter of the inhibition of bacteria by taking a picture of a 15cm ruler on

   
   

   the petri dish with black background behind the petri dish and take photos
   
   
2. calculate the area of the inhibition zone from photos making sure it is to scale
   
   
3. Plot a histogram of the area of the inhibition zone to the concentration of Clorox.
   
   
4. Plot a graph of inhibition zone against concentration of Clorox. 
   
   

4. Risk Assessment and Management: Identify any potential risks and safety precautions to

be taken.

Table 1: Risk Assessment and Management table