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

2. 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

3. 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

4. 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

5. 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.

6. 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.

7. 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

8. 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.

9. 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.

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

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

12. 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.

13. 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

14. 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.

15. 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

16. 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

17. Works Cited https://www.ncbi.nlm.nih.gov/pmc/articles/PMC101483/

18. E.Coli ANOVA

19. Staphylococcus ANOVA