SCHOOL OF SCIENCE AND TECHNOLOGY, SINGAPORE
INVESTIGATIVE SKILLS IN SCIENCE
Names: Elysia Ho, Zin Mi Myint Thein, Rachel Wong
Group Reference: B
A. Indicate the type of research that you are adopting:
[ X ] Test a hypothesis: Hypothesis-driven research
Type of research: 1 (Write down one number from 1 to 6)
Category – 10 (Write down one number from 7 to 20)
Sub-category – b (Write down the sub-heading alphabet)
Application of project relevant to SST Community, Society or the World:
If these cleaning agents could remove 100% of bacteria, we could possibly use it in the hospital to cleanse our hands before an operation to minimise the risk of infection.But if the cleaning agents are not effective we can test on other cleaning agents and find out if they are also effective.
C. Write down your research title:
Investigation of the effects of different cleaning agents on killing bacteria.
D. (a) Aim / question being addressed:
The cleaning products we would be using are:
- Mama Lemon
As written above in Dettol’s website, their brand started 80 years ago, therefore making them an experience company in the field of cleaning agents.
As it said in the advertisement above, its kills 99.9% of bacteria.
Lifebuoy said that it also kills 99.9% of germs as well, what’s more, only in 10 seconds.
Also below, it shows when Lifebuoy has been around for around 200 years.
This is taken from the mama lemon website, stating that it get rids of 99.9% of bacteria as well.
Above, proof that Mama lemon has been around over a 100 years.
As mentioned above in Clorox’s website, they have been in this industry for the past 100 years! Making them even more experience as compared to Dettol.
Also, they said that they kill 99.9% of germs.
E. coli stands for Escherichia coli, and refers to a group of bacteria that are commonly found in food and water. Most of these bacteria are harmless, but some can cause sickness. Those that cause disease do so by creating the Shiga toxin, which makes people sick. This toxin most commonly leads to stomach and intestinal problems, such as diarrhea and vomiting. Some people can get infections that become life-threatening, while others recover after about a week. Children, those with immune system disorders, and the elderly are at the highest risk of facing a life-threatening case of E. coli.
(b) Independent variable
The independent variable Brand of antibacterial agent used (Dettol, Lifebouy, Mama Lemon, Clorox)
(c) Dependent variable
The of bacteria killed
(d) Controlled variables
- the ml of cleaning agent used.
- one type of agar (E.coli)
- ml of agar.
- ml of bacteria in each petri dish.
- ml of petri dish (filled with agar).
- Surrounding that the petri dish is left in. (a warm, dark place)
Dettol can kill more bacteria as compared to the other cleaning agents. We believe that Dettol is the best cleaning agent product among all.
E. Method – Description in detail of method or procedures (The following are important and key items that should be included when formulating ANY AND ALL research plans.)
(a) Equipment list:
- Test tube rack
- Bacterial incinerator
- Sterile swabs
- Two Mueller-Hinton agar plates
- Antibiotic disks – each pair of students will be using:
- (i) TWO different antibiotics
- (ii) Antibiotic-free disks (BLANK)
- Stock broth cultures of: -
- Escherichia coli (Gram negative)
(on page 5)
(c) Procedures: Detail all procedures and experimental design to be used for data collection
- Label the agar plates with the usual 5 items. Also mark, using dots, where you will put the the BLANK disk. b. Disks should not be placed near the edge of the plate
- Inoculate one plate with your first bacterium as follows:
- Using the Aseptic Technique , spread the E.coli using the Spreader evenly
- Place one blank disk onto the surface of the agar
c. Carefully pick up your test disk with the forceps, and gently place it in the appropriate spot on the agar surface,
d. To ensure that the disk is flat on the agar, gently push it down with the forceps.
e. Reheat the tips of the forceps as above to kill any bacteria.
- Repeat the procedure with the second antibiotic disk.
- Repeat the procedure with the BLANK disk.
- Repeat steps 1 – 6 on a new agar plate with your second bacterium.
- Wait until the surface of the plates has completely dried (it may help to leave the lid slightly open for 3 - 5 minutes).
- Incubate both plates at 37C
- Will be recording diameter of the zone of inhibition in mm (see the two figures below), and record your results in the Table on the next page. If there is no zone present, record your result as 0 mm.
Specify any potential risks and safety precautions to be taken.
As the experiments involve heating, there is a risk of fire if the flame accidentally touches any flammable material.
Make sure that there are no flammable materials near the heating apparatus, and not to burn ourselves.
Handling the bacteria in the petri dishes would be necessary, risk of infection is high.
Wearing a glove would decrease the risk of infection through handling the petri dishes/bacteria.
Handling cleaning agents might cause skin discomfort.
Wearing a glove would avoid this from happening.
Soap might spill on the floor causing others or ourselves to fall.
Clean up immediately after spillage.
Table 3: Risk Assessment and Management table
(e) Data Analysis: Describe the procedures you will use to analyze the data/results that answer research questions or hypotheses
Cleaning agent 1
Cleaning agent 2
Cleaning agent 3
Cleaning agent 4
Without cleaning agent
Ecoli disk (1)
Ecoli disk (2)
Ecoli disk (3)
Ecoli disk (4)
Ecoli disk (5)
- Compare all the values written on the table
- Using the number of colonies in each petri dish of antibacterial agent, express it as a percentage of the number of colonies in the control petri dish.
- Using the number of colonies found in each petri dish, plot two bar graphs (Number of colonies and percentage of colonies) to analyse the data. The lowest “bar” is the most efficient antibacterial agent out of all the agents chosen.