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Science Fair Project: Where In The School Can You Find The Most Bacteria?

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Shalin Patel

on 24 January 2013

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Transcript of Science Fair Project: Where In The School Can You Find The Most Bacteria?

By: Shalin Patel
Physics S/T, 1B
Mr. Andy Infested Corners Question Where in the school can you find the most bacteria? Hypothesis • If I collect bacteria samples from various locations from the school, then the bacteria samples from the cafeteria will grow the most bacterial colonies out of all the other locations in the school. Materials •Nutrient Agar (3.45 grams)
•Water (150 mL)
•100 mL measuring tube
•6 Petri dishes
•Sterile cotton swabs (about 6 at least)
•A glass beaker
•A measuring scale
•A small tray
•A spoon
•A magnetic stirrer
•A hot plate
•An incubator
•A marker
•A plastic bag
•Clorox Variables • Independent Variable: The locations from which the bacteria samples came

• Dependent Variable: The colonies that grow from the specific bacteria samples.

• Controlled Variable: The Petri dishes, the amount of nutrient agar and water used in each Petri dish, sterile cotton swabs, and the incubator. Procedures 1. I placed the magnetic stirrer into the glass beaker.

2. I poured 150 mL of water using the 100 mL measuring tube into the glass beaker.

3. I measured 3.45 grams of nutrient agar by putting a small tray on the measuring scale and then zeroing it. I kept adding nutrient agar into the tray using a spoon until the measuring scale measures 3.45 grams.

4. Then I added the 3.45 grams of nutrient agar into the glass beaker, and then placed the glass beaker on top of the hot plate.

5. I turned the hot plate on to a high temperature and then turned the knob for magnetic stirring to a high speed to allow the water and nutrient agar to mix completely while they boil.

6. I waited until the mixture achieved a rolling boil and then turned the hot plate off completely in order to allow the mixture to cool off.

7. Once the mixture cooled off a bit, I took the lids off the Petri dishes and poured equal amounts of the mixture into of them. I made certain not to overfill the Petri dishes.

8. I placed the lids back on the Petri dishes and allowed them to cool off completely into a jelly like form.

9. Once the Petri dishes were done cooling, I collected bacteria samples from at least 6 locations in the school by using sterile cotton swabs and swabbing the floor of each location. I made sure to take one Petri dish and collect one bacterial sample at a time in order to prevent a mix up in samples.

10. Once I collected the bacteria sample per location, I rubbed the sterile cotton swab with the sample in a zigzag formation over the agar in the Petri dish and then closed the lid.

11. Once all of the Petri dishes have the bacteria samples in them, I placed them in an incubator and allowed the bacteria samples to grow for at least 24 hours.

12. Once 24 hours have passed, I took out the Petri dishes and counted the amount of bacterial colonies that grew in each dish by using a marker to mark each individual colony to prevent over or under counting.

13. When all of the bacterial colonies have been counted in each Petri dish, I compared the results and saw which Petri dish contained the most bacteria colonies. The sample that contained the most bacterial colonies is the location where you can find the most bacteria.

14. After the data had been collected and recorded, I poured a small amount of Clorox into each Petri dish and mixed it around. Once the Clorox is\was mixed around with the bacterial colonies, I disposed of the Petri dishes in a plastic bag. Data Pictures Data Analysis/Results •From the chart, the girl’s bathroom contained the most bacterial colonies or CFU’s (Colony forming units) with 60 CFU’s, while the auditorium contained the least amount of bacterial colonies with 16 CFU’s. The boy’s bathroom (38 CFU’s) and the cafeteria (39 CFU’s) were almost the same in the amount of CFU’s, while the library (25 CFU’s) and lobby (18 CFU’s) had a generally low amount of bacterial colonies compared to the rest. From these results, I can conclude that the girl’s bathroom is the area in the school where you are expected to find the most bacteria. Conclusion • My experiment was successful and I was able to complete it with little to no errors. Everything that I expected to happen in my experiment occurred except for my hypothesis. I predicted that the cafeteria would contain the most bacteria due to the fact that bacteria grows in messy and warm areas, which makes the cafeteria an ideal place for bacteria to thrive. After my experiment, I concluded that the girl’s bathroom contained the most bacterial colonies with 60 CFU’s compared to the cafeteria’s 39 CFU’s. It turned out that my assumption of the cafeteria being an “ideal” place for bacteria to thrive was incorrect because the cafeteria in fact is quite cold and not warm, which may have been why there was less bacterial colonies there than expected. If I were to do this experiment again, I would choose new locations to collect samples from and compare my results. Instead of counting the individual bacterial colonies, I would look into finding a more accurate way of measuring the amount of bacterial colonies in a sample. In conclusion, my hypothesis was incorrect, but I learned a lot from my experiment and gained a lot of hands on experience with lab equipment and general data collecting. Acknowledgments • I would like to thank my physics teacher, Mr. Andy, for approving my science fair topic and guiding me in completing my science fair research and report.

• I would like to lastly thank my supervisor, Mr. Sharif, for giving me the materials needed to complete my experiment and for guiding me in actually completing my experiment itself. The End! Real World Application My project can apply to the real world because it's used in testing the cleanliness of an area. Most health inspectors test for bacteria counts in a food establishment before allowing that establishment to serve food to people. Overall, my project is useful in finding out whether an area is safe to be in or not. Some areas may contain harmful bacteria that can affect someone's health, which is crucial to know and my project can help find that out.
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