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What Effect Do Microwaves Have on Microbes

Study on whether microwaves reduce microbial contamination. Results showed a significant reduction in colonies, especially in Staph.

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What Effect Do Microwaves Have on Microbes

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  1. What Effect Do Microwaves Have on Microbes By: Matthew Scholl 9th grade Representing: Central Catholic High School, Pittsburgh 3rd year participating in PJAS

  2. Do microwaves have an adverse impact on microbes; such as Staph and E-coli? Purpose

  3. Implications • Is microwave cooking effective at reducing microbial contamination?

  4. Microwaves-Long electromagnetic non-ionizing waves that range from 1mm to 1m. Frequency can reach 2.45 billion hertz.Frequency harmful to humans starts at 10,000 hertz. Thermal affect- Microwaves heat food by vibrating food molecules so fast they create friction as heat. Microwaves

  5. Escherichia coli • Diverse and large group of bacteria • Found in the intestines of most mammals • Strains are mostly not pathogenic • Some produce shiga damaging lining of intestines • Gram (-)

  6. Staphylococcus epidermidis • Bacteria found on healthy human skin • Most forms not pathogenic • Gram (+) • Can cause Staph infection upon entry into body

  7. Independent Variable-Seconds of microwave exposure.Dependent-Amount of colonies that survived.Control-0 seconds of exposure time. • Variables

  8. Null-Microwaves will have no significant effect on microbial survivorship.Alternate- Microwaves will significantly reduce microbial survivorship. Hypothesis

  9. Materials • • 64 LB Agar Plates (0.5% yeast extract, 1% tryptone, 1% sodium chloride. • Peristaltic Pump • Flask • Sterile Dilution Fluid [SDF] (100mM KH2PO4, 100mM K2HPO4, 10mM MgSO4, 1mM NaCl) • Spreader bars • Incubator • Alcohol • Bunsen Burner • Escherichia coli (DH5-alpha) • Staphylococcus epidermidis • Micropipets • Camera (on Phone) • Notebook • Sharpie • Holding stand (For Flask) • Racks • Sterile test tubes • Old General Electric turntable oven (8,500 Watts.)

  10. Liquid Exposure Trials • The approximate density of the initial Staph and E. coli epidermis was 10^8 cells/ml. • Bacteria were diluted to a concentration of 10^5 cells/ml. • The cells were then added to sterile dilution fluid, resulting in a final concentration of 10^3 cells/ml. • Equivalent tubes microwaved to temperatures of 0, 5, 10, 15, 20 seconds.

  11. Sterile water tubes were microwaved for the previous exposures to determine temperature change. Thermometer Data Collection

  12. Pipetted .1ml the first solution into 30 plates.Spread all solutions with spreader bars.Microwaved 5 plates for each exposure.0 seconds5 seconds10 seconds 15 seconds20 seconds 30 secondsPlates were incubated at 37 Celsius.Colony survivorship was recorded. Solid Exposure Trials

  13. Not Significant P= 0.00078 Not significant T crit=3.29 Y=Surviving Colonies Significant significant

  14. P Value 0.000124 T Crit=3.29 Not Significant Y=Surviving Colonies Significant Significant Significant

  15. P Value=0.014 T Cit=3.62 Y=Surviving Colonies Significant Significant Significant Significant Significant

  16. Solid Microwave Plate Staph Exposure Y=Surviving Colonies P Value=6.18E-09 T Crit=3.62 Significant Significant Significant Significant Significant

  17. Y=Survivorship of Colonies Tube E-coli. Tube Staph. Plate E-coli. Plate Staph

  18. Nullhypothesis rejected- both bacteria’s survivorship were significantly reduced at the higher microwave exposures.Null rejected on Staph liquid exposure for 15 and 20 seconds.Null rejected on E-coli liquid exposure for 10, 15, and 20 seconds.Null rejected on Staph solid exposure for all trials except the control.Null rejected on E-coli solid exposure For all trials except the control.Alternate accepted-Microwave exposure significantly affected the survivorship of colonies. The more seconds of exposure=less colonies that survive. Conclusion

  19. Explanation Plate survivorship reduced most because water had a protective effect in absorbing microwave energy. Staph colonies decreased least. Gram (+), thicker peptidoglycan layer, Cell wall more resistant to heat and antibiotics. Microwaves reduced survivorship, heated microbes, destroying- mutating proteins that make reproduction possible.

  20. Limitations • Study does not reveal other effects on the colonies health • Use different concentrations • A difficulty in synchronizing exposures and plating • Narrow ranges of exposure

  21. Extensions/ Improvements • Use more trials • Wider range of exposures in power and time • Test on actual food • Use many other different species of bacteria, salmonella, shingella, streptococcus

  22. Lucas, Jim. “What Are Microwaves?” LiveScience, Purch, 8 Feb. 2018, www.livescience.com/50259-microwaves.html.“Microwaves.” The Electromagnetic Spectrum: Radio Waves, www.darvill.clara.net/emag/emagmicro.htmFischetti, Mark. “How the Microwave Works.” Scientific American, 1 Nov. 2008, www.scientificamerican.com/article/how-the-microwave-worksCenter for Devices and Radiological Health. “Resources for You (Radiation-Emitting Products).” U S Food and Drug Administration Home Page, Center for Drug Evaluation and Research, www.fda.gov/radiation-emittingproducts/resourcesforyouradiationemittingproducts“How Does a Microwave Oven Cook Foods? Is It Harmful If Some of the Microwave Radiation Leaks out and Hits the Skin?” Scientific American, www.scientificamerican.com/article/how-does-a-microwave-oven/.“Staphylococcus Aureus.” Wikipedia, Wikimedia Foundation, 19 Jan. 2019, en.m.wikipedia.org/wiki/Staphylococcus_aureus“Staphylococcal Infections.” MedlinePlus, U.S. National Library of Medicine, 4 Dec. 2018, medlineplus.gov/staphylococcalinfections.html.“E. Coli (Escherichia Coli) | E. Coli | CDC.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, www.cdc.gov/ecoli/index.html“Agar.” Wikipedia, Wikimedia Foundation, 20 Jan. 2019, en.m.wikipedia.org/wiki/Agar“Javascript Required!” Nuclear Power in Canada - World Nuclear Association, www.world-nuclear.org/nuclear-basics/what-is-radiation.aspx“What Is the Electromagnetic Spectrum?” EarthSky, earthsky.org/space/what-is-the-electromagnetic-spectrum. • Bibliography

  23. dunetts testsStaph Tube

  24. dunetts E-Coli tube

  25. Dunetts Plate E-Coli

  26. Dunetts test plate Staph

  27. Plate Staph Anova Plate E-coli Anova

  28. Tube E-Coli Tube Staph

  29. Average SurvivorshipIn E-coli tubes: one plate had 31 colonies and another 18 • E-coli plates 7, 13.

  30. Background Microwaves • Microwaves for cooking-Microwaves produced by a magnetron. Two parts are opposite magnets. Create magnetism dislodge electrons from air. • Microwaves are amplified and are repeatedly bounces of the inside of the microwave. • Thermal affect- Microwaves heat food by vibrating food molecules so fast they create friction as heat.

  31. Radiation-Movement of energy as waves or particles through a medium. Electromagnetic Radiation-Uses electrons and magnetism and consists of; Radio waves,Microwaves, visible light, x-Rays, etc.. Background-Radiation

  32. Electromagnetic Spectrum-The entire range of wavelengths. Background-Radiation

  33. Gram positive- Do retain Chrystal violate stain in the gram method. Prokaryotic, thick PEPTIGLOGLYCAN layer, strong cell wall, more heat resistant.Eubacteria- simple cells, round shaped, rigid cell walls, and use flagellum for movement. • Background Staphylococcus Epidermytis

  34. Staph Infection • Staph infection- An infection on skin or respiratory tract warts or large boils. fatal when in blood stream.

  35. Gram negative- opposite of Gram positive, weak cell wallProkaryotic- no nucleus or membrane bound organellesUnicellular and rod-shapedProteobacteria- Reproduce rapidly and have many pathogens Escherichia Coli

  36. Lives in intestinal tract and usually harmless.Some strains produce shiga, damaging lining of intestines. food poisoning, Pneumonia, and urinary tract infections. Thermal affect- Microwaves heat food by vibrating food molecules so fast they create friction as heat E.coli Disease

  37. Materials Continued • Staphylococcus Epidermidis • Petri dishes • Camera (on Phone) • Notebook • Sharpie • Holding stand (For Flask) • Racks • Sterile test tubes • Old General Electric turntable oven.

  38. • 64 LB Agar Plates (0.5% yeast extract, 1% tryptone, 1% sodium chloridePeristaltic PumpFlask Spreader barsIncubatorAlcohol Burner• Escherichia Coli (DH5-alpha) Materials Peristaltic Pump

  39. P value always less than .05- There was significant variation between groups.Dunetts test, t value greater than t crit.(significant variance)Large difference between the groupings, the radiation had an affect on survivorship.Small difference within groups scientist can trust the results. The P value, Dunetts test, and other statistics show significant variances rejecting the null. • Statistics

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