2. Methods


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.


Fig 4; Our working environment- bio-safety cabinet.

















B)Making The Streak Plate Culture


5. Prepare 4 bacteria sample(Escherichia coli,B subtilis)


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.



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 37ยบ C.


D) Preparing to Test the samples.

12. Prepare some nutrient broth in a test tube. 

13. Extract some nutrient broth with a pipette to a test tube




Fig 6; Pipette with 50 micro lite adjustment.






















14. After incubation of bacteria, scoop one of the colonies with an inoculation loop and dip it inside the test tube with the nutrient broth and mix it.

15. Prepare about 50 L spreaders and petri dishes. Use a pipette and transfer 50 micro liter to petri dish and use a L spreader to spread until the mixture for about 20 seconds in random directions


Fig 7: L Spreader

















16. Label Petri dish- (type of bacteria, time exposed)


E)UV light source



17. Remove the lid of the petri dishes and expose to UV light source. there were a total of 26 dishes.

2 dishes - E coli and B subtilis not exposed for UV
3 dishes- E coli exposed for 15 mins
3 dishes-  E coli exposed for 30 mins
3 dishes-  E coli exposed for 45 mins
3 dishes-  E coli exposed for 60 mins

3 dishes - B subtilis exposed for 15 mins
3 dishes - B subtilis exposed for 30 mins
3 dishes - B subtilis exposed for 45 mins
3 dishes - B subtilis exposed for 60mins

Fig 9: B subtilis labeled and ready for exposure.
















Expose all these dishes according to their respective time.
Fig 10:Dishes getting exposed to UV.
















18. After exposure, seal petri dishes with para film.

19. Place the petri dishes into the incubator to let it grow.

F) Data Collection

20. Take pictures of the samples and collect the data, observe how the UV affected the growth of bacteria.


• 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 a stopwatch to time how long each bacteria is exposed to UV light   
3.   Count the bacteria in a petri dish after it is left to grow after a day
4.   Make a table to plot which bacteria grew the most in the given time(0, 15, 30, 45, 60) and classify them by the time it was exposed UV light and their concentration of colonies in one petri dish
5.   From the table we can find out if our hypothesis is correct

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