Group Project Proposal (Science)
SCHOOL OF SCIENCE AND TECHNOLOGY, SINGAPORE
INVESTIGATIVE SKILLS IN SCIENCE
Names: Tony Zhang, Myo Nyi Nyi
Group Reference: F
1. Indicate the type of research that you are adopting:
[ X ] Measure a function or relationship: Experimental research (II)
2. Write a research proposal of your interested topic in the following format:
Title: An investigation of the exposure of UV ray on the growth rate of bacteria
Our research aims to find out the relationship between the duration of UV exposure to bacteria and the growth rate of it. Other research shows that Mutations are a heritable change in the base sequence of DNA. We learned previously that some mutations can be neutral or beneficial to an organism, but most are actually harmful because the mutation will often result in the loss of an important cellular function.It is known that UV rays kills bacteria easily but very few know the exact time UV rays kills bacteria. In our experiment we will be using two types of bacteria (Escherichia coli,Bacillus subtilis), our research objective is to test the how long each bacteria lasts under the exposure of UV ray. We will be culturing these bacteria by using the Streak-Culture method.Bacterial culture streaking allows bacteria to reproduce on a culture medium in a controlled environment. The process involves spreading bacteria across an agar plate and allowing them to incubate at a certain temperature for a period of time. Bacterial streaking can be used to identify and isolate pure bacterial colonies from a mixed population. We would keep one type of bacteria as a control to see how bacteria grows overtime without the UV ray exposure. Place the plate, agar side up, into an incubator for 48 hours at 37º C. Upon proper completion of the process, a pure culture of bacteria will be obtained. The third section of the plate will have individual colonies and the plate will be completely free of contamination. Now that we have a pure culture, biochemical tests can be performed. As microbiology students, perfecting the streak plate method for obtaining a pure culture of bacteria is of utmost importance and will be used to perform our experiment accurately and obtain precise results. We would then be using these cultured bacteria to expose it under the UV light source in a dark room so other lights will not interfere with our experiment. Using a bacterial colony counter, we will be able to collect the data and tabulate it together to draw a table and a graph to see the difference and prove our hypothesis. From this experiment we would understand more on how UV affects the growth of bacteria and would be able to find out how UV exposure affects the growth rate of the bacteria.
An investigation on the effect of UV ray on different types of bacteria
A. Question being addressed
We wanted to find out if UV ray changes the rate of bacteria growth.
The independent variable: Growth rate of bacteria
The dependent variable: Time bacteria is exposed to UV ray
The constants variable:
Intensity of UV ray
The amount of bacteria exposed to UV ray
Size of petri dish
Time each bacteria is allowed to grow
Humidity of environment around bacteria
Distance between the bacteria and the UV light source
The longer the bacteria is exposed to the UV light source, the slower the bacteria will grow and sometimes even killed if exposed for too long.
C. 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.)
-UV light source
-Bacterial colony counter
-Petri dish (60)
-Disinfectant(10% bleach or 70% ethanol)
• Procedures: Detail all procedures and experimental design to be used for data collection
Procedures are adapted and retrieved from Ryan Heasley (12/07/2009 ).
Preparing a Pure Bacterial Culture of Bacteria on a Nutritive Agar Plate
A)Creating A Sterile Environment
1. Wash hands to remove any bacteria present on hands using warm water and soap. Rinse hands with a towel thoroughly and turn the of the tap using the towel.
2.To maintain a sterile environment and protect ourselves from potential pathogens, put on a latex glove.
3.Use bleach to kill off any bacteria present on the workbench.
4.Assemble a bunsen burner to sterilize any equipment during the experiment and keep the air clean. Make sure the gas is turned off at all times except when the
flame is lit to ensure gas does not diffuse into the air, which is harmful to inhale and
can also ignite in the presence of any spark.
B)Making The Streak Plate Culture
5. Prepare 4 bacteria sample(Escherichia coli,Lactobacillus acidophilus,Streptococcus,Spirillum volutans).
6. Prepare 5 petri dishes with nutrient agar.
7. Sterilise the inoculation loop with the flame of the bunsen burner.
8. Using the inoculation loop, dip it into the test tube with the bacteria sample and make a primary streak on the petri dish.
<Primary streak like this. Flame the inoculation loop and cool it again.
<Streak to the right 4 times from the primary bacteria streak.Flame the inoculation loop and cool it again.
<Streak down to the right side 4 times. Flame the inoculation loop and cool it again.
<Streak downwards. Flame the inoculation loop and cool it again.
<Make zig zag lines and close the petri dish.
Pictures and procedures are adapted above are adapted from URMICRO1 (29/9/2010)
Isolation of bacterial colonies
C)Incubating The Streaked Nutritive Agar Plate.
9. Place the plate back onto the lid of the plate and seal it with a tape.
10. Label all the plates( what bacteria ? what duration is it going to be exposed for ? )
11. Place the plate, agar side up, into an incubator for 48 hours at 37º C.
D)UV light source
12. Putting the the plates under the UV light source for 15min, 30min, 45min and 60 min and one plate not under UV light source for experiment control.
13. Collect the data and tabulate it together.
• Risk and Safety: Identify any potential risks and safety precautions to be taken.
As we are using different types of bacteria in the project, must be sure to use gloves when handling.
We need a sterile environment when we handle with bacteria, we must sterilise the equipments before and after use.
Disinfect work area before and after use, Using a disinfectant, such as a 10% bleach or 70% ethanol solution, to wipe down work areas both before and after working with cultures.
Any spillage bacteria, whether a drop or an entire culture, place paper toweling over the spill to absorb it. Without letting your hand touch the absorbed liquid, place the paper towel into the "biological waste" container. Disinfect the area thoroughly. Wash your hands thoroughly with disinfectant and soap.
Label every culture to make sure that we do not use the wrong culture. If they are hazardous, label them with proper warning and hazard information.
As we are using UV light which is harmful to human skin, we should be careful about the time we expose ourselves to the light.
• Data Analysis: Describe the procedures you will use to analyze the data/results that answer research questions or hypotheses
1. Use the auto timer switch to control how long each bacteria is exposed to UV light
2. Count the remaining bacteria after UV exposure in each petri dish and plot a table according to each petri dish for each try
3. Count the bacteria in a petri dish after it is left to grow after 2 day with bacterial colony counter
4. Make a table to plot which bacteria grew the most in the given time(0, 10, 15, 30, 45) and classify them by the time it was exposed UV light
5. From the table we can find out if our hypothesis is correct
D. Bibliography: List at least five (5) major references (e.g. science journal articles, books, internet sites) from your literature review. If you plan to use vertebrate animals, one of these references must be an animal care reference. Choose the APA format and use it consistently to reference the literature used in the research plan. List your entries in alphabetical order.
Michelle Furlong,(16 July 2014) Effects of UV Light Exposure on Bacteria.
Retrieved it from
Paul Hörtnagl, María Teresa Pérez, and Ruben Sommaruga,(March 1, 2011) Contrasting effects of ultraviolet radiation on the growth efficiency of freshwater bacteria
Retrieved it from
Alyssa E. Beck,(2004) What Are the Effects of Ultraviolet Light on Bacteria Mortality
Retrieved it from
David B. Fankhauser,(15 July 1991) ULTRAVIOLET KILLING OF BACTERIA
Anne Rammelsberg,(17 Aug, 1998) How does ultraviolet light kill cells?
URMICRO1,(29 Sep, 2010) Isolation of bacterial colonies
Regina Bailey,(16 July, 2014) How To Streak a Bacterial Culture
Ryan Heasley,(12 July, 2009) Preparing a Pure Bacterial Culture of Bacteria on a Nutritive Agar Plate