Effects of Microwave Radiation on Bacteria Liam Kearney Grade 9 Pittsburgh Central Catholic High School 1st Year Participating in PJAS

MICROWAVE RADIATION Non-ionizing set of electromagnetic waves Ranges from one meter to one millimeter Frequency within a microwave can reach 2.45 billion hertz Form of radio frequency radiation Frequency shown to start harming the human body is only 10 hertz Studies suggest that long-term exposure can have a mutagenic effect

ESCHERICHIA COLI (E.COLI) Large and diverse group of gram (-) bacteria Free living, symbionts, and pathogens Live in the intestinal tract of many mammals Most strains are not pathogenic Serve as a common prokaryotic cell model

STAPHYLOCOCCUS EPIDERMIDIS (STAPH) Common surface symbiont in many mammals (Human) Gram (+) bacteria Most strains considered non-pathogenic Pathogenic strains can be life-threatening Prokaryotic cells

PURPOSE The purpose of this experiment is to observe the effects of the varying exposure times of microwave radiation on the survivorship of E.coli and Staphylococcus Epidermidis.

HYPOTHESES Null Hypothesis: The differing exposure times of microwave radiation will not significantly affect the survivorship of E.coli and Staphylococcus. Alternative Hypothesis: The differing exposure times of microwave radiation will significantly affect the survivorship of E.coli and Staphylococcus.

MATERIALS Sterile Dilution Fluid-100mM KH2P04, 100mM K2HPO4, 10mM MgSO4, 1mM NaCl Macropipette- Sterile Tips Micropipette- Sterile Tips 10 Test Tubes- 5=E.coli, 5=Staph Test Tube Racks Vortex Microwave (60 hertz) YEPD Agar Petri Dishes-1% yeast extract, 2%peptone, 2% dextrose Ethanol Bunsen Burner Sterilized Spreader Bars Incubator C600 Escherichia coli Staphylococcus epidermidis

PROCEDURE Cultures of each bacteria were grown overnight. Both bacterias were grown until a density of 50 klett spectrometer density was reached. This was approximately 10^5 cells/mL. The culture of cells was diluted to a concentration of 10^3 cells/mL in the sterile dilution fluid of 10mL per tube.

PROCEDURE (continued) The tubes were labeled: o sec., 5 sec., 10 sec.,15 sec., and 20 sec. for both bacterias. The tubes were vortexed and placed into a microwave for the selected time 0.1 mL from each tube were plated onto 4 YEPD agar plates each. The plates were incubated for 2-3 days at 37°C.

LD50 E.coli: About 7 sec. Staph: About 6 sec. P-Value E.coli: less than 10^-6 Staph: less than 10^-6

P-Value E.coli: less than 10^-6 Staph: less than 10^-6

STATISTICAL ANALYSES ANOVA Using the ANOVA, if a p-value less than the alpha of 0.05 is generated (significant variation), it suggests that the null hypothesis can be rejected Dunnett's Test A 0.05 alpha was used, and each generated T-value was compared to the T-critical value of 2.78 If the T-value> the T-critical, than the results are significant.

Dunnett's Test Results Microwave Exposure Time T-Value T-Crit Variation E.coli 5 seconds 4.605 2.78 SIGNIFICANT 10 seconds 12.591 15 seconds 15.579 20 seconds Staph 11.828 25.828 30.663 30.745

Conclusion/ Interpretation The null hypothesis is rejected for both bacterias as they were both significantly affected by the microwave radiation The ANOVA analyses showed that microwave radiation had a significant effect on both bacterias as both of the p-values were less than 0.05. The Dunnett's Tests showed that each exposure time had a significant effect on both bacterias.

Limitations Different species of bacteria could have been used Additional concentrations could have been used More replicates could have been used to supply more accurate evidence Power of Microwave? Only 10 mL tubes were used

Extensions Use of more species of bacteria Use different concentrations Use more replicates Use a more/less intensive microwave Use a greater volume of liquid

Works Cited https://www.ncbi.nlm.nih.gov/pmc/articles/PMC101483/ http://www.medicinenet.com/staph_infection/article.htm https://www.foodsafety.gov/poisoning/causes/bacteriaviruses/staphylococcus/ https://www.gstatic.com/healthricherkp/pdf/staph_infection.pdf http://www.webmd.com/a-to-z-guides/tc/e-coli-infection-topic-overview#1 http://www.cancer.org/cancer/cancercauses/radiationexposureandcancer/radiofrequency-radiation http://www.livescience.com/50259-microwaves.html https://www.ncbi.nlm.nih.gov/pmc/articles/PMC101483/

E.Coli ANOVA

Staphylococcus ANOVA