1. The Effects of Hydrochloric Acid and UV Radiation on E. Coli
David Foody
Central Catholic High School
Grade 9

2. Escherichia coli (E. coli)
Large and diverse group of gram (-) bacteria
Free living, symbionts, or pathogens
Most strains are not pathogenic
Serve as a common prokaryotic cell model
Common mammalian intestinal symbiont
Environmental prokaryotic model

3. Electromagnetic Spectrum
Diagram showing the range of all types of frequencies of electromagnetic radiation
The types of radiation are radio waves, microwaves, infrared, visible, ultraviolet, x-rays, and gamma rays

4. Ultraviolet Radiation
Ultraviolet (UV) rays are light rays that have shorter wavelengths than visible light
Range from 150nm – 300nm
They are naturally given off by the sun, but most are absorbed by the ozone layer
The wavelength used in this experiment is 254nm light

5. pH Measures how acidic or basic a substance is Scale from 0-14
pH Scale
Neutralization
Measures how acidic or basic a substance is
Scale from 0-14
pH < 7 acidic, pH > 7 basic, pH = 7 neutral
The mixture of an acid and a base.
Mixture of acid and base commonly yields water

6. Hydrochloric Acid
Forms an organic salt when it reacts with an organic base
Strong mineral acid
pH level of 3
Highly corrosive
Often used to restore metals

7. Purpose
Test the survivorship of E. Coli when exposed to Ultraviolet Radiation and Hydrochloric Acid.
Determine if radiation from the sun affects the refinements of ores

8. Question
Will differing amounts of Hydrochloric Acid and ultraviolet radiation have a significant effect on E. Coli?

9. Hypothesis
Null Hypothesis: The Hydrochloric Acid and ultraviolet Radiation will not have a significant effect on the resulting amount of E. Coli.
Alternative Hypothesis: As the concentration of Hydrochloric Acid and exposure to ultraviolet radiation increases, the survivorship of the E. Coli will decrease.

10. Materials LB Agar Plates Spreader Bars Ethanol Matches
Hydrochloric Acid (HCl)
Water
Escherichia Coli
UV Lamp (254 nm)
Incubator
Test Tubes
Stopwatch
Vortex Machine
PH Strips
Sterile Dilution Fluid

11. Procedure Bacteria (E. Coli) was grown overnight in LB Media
A Sample of the Overnight Culture was added to fresh media in a Sterile Sidearm Flask
The Culture was placed in an incubator until a density of 50 Klett spectrophotometer units was reached. This represents a cell density of approximately 108 cells/mL.
The culture was diluted in sterile dilution fluid to a concentration of approximately 108 cells/mL.
Various concentrations of Hydrochloric Acid were created in test tubes containing SDF, resulting in 9.9 mL per tube

12. Concentrations pH of 0 pH of 5 pH of 3.5 mL of E. Coli 0.1 mL
mL of Water
8.9 mL
mL of Acid
0 mL
0.55 mL
mL of SDF
1 mL
0.9 mL
0.45 mL
Total Volume
10 mL K

13. Procedure (Continued)
0.1 ml of E. Coli was then added to the test tubes, yielding a final volume of 10 mL.
The solutions were mixed by vortexing and allowed to sit at room temperature for 10 minutes.
After vortexing to evenly suspend cells, 0.1 ml was removed from the tubes and spread on LB plates.
Plates were then placed under a UV lamp for specific times (3 seconds and 6 seconds)
The plates were incubated at 37°C for 24 hours
The resulting colonies were counted. Each colony is assumed to have arisen from one cell.

14. E. Coli Colonies with No Radiation Results

15. Individual Stat Analysis
T-Value/P-Value
T-Crit
Significant/Not Significant
pH 5 vs control
T = 3.35
3.06
Significant
pH 3 vs control
T = 6.94
pH 5 vs pH 3
P =

16. E. Coli with 3 Second Radiation Results

17. Individual Stat Analysis
T-Value/P-Value
T-Crit
Significant/Not Significant
pH 5 vs control
T = 3.61
3.06
Significant
pH 3 vs control
T = 5.92
pH 5 vs pH 3
P =

18. E. Coli with 6 Second Radiation Results

19. Individual Stat Analysis
T-Value/P-Value
T-Crit
Significant/Not Significant
pH 5 vs control
T = 4.92
3.02
Significant
pH 3 vs control
T = 7.04
pH 5 vs pH 3
P =

20. Conclusion
Null hypothesis: The Hydrochloric Acid and ultraviolet Radiation will not have a significant effect on the resulting amount of E. Coli.
Null Rejected
All colonies exposed to Ultraviolet Radiation and Hydrochloric Acid had a significant effect.
The longer the E. Coli was exposed to UV Radiation and the lower the pH level of Acid, the lower the E. Coli survivorship

21. Future Experimentation and Limitations
More pH levels and times for UV Radiation could be used
Use different chemicals
Use other sources of radiation
Some sunlight was shining into the room while spreading the plates
Only 1 species tested
Only survivorship was tested

22. Sources
Website Title: Centers for Disease Control and Prevention Article Title: E.coli (Escherichia coli) Publisher: Centers for Disease Control and Prevention Electronically Published: January 25,
Website Title: Healthline Article Title: E. Coli Infection: Causes, Symptoms, and Prevention Publisher: Healthline Media
Website Title: National Center for Biotechnology Information. PubChem Compound Database Article Title: hydrochloric acid Publisher: U.S. National Library of Medicine
Website Title: HYDROCHLORIC ACID, SOLUTION | CAMEO Chemicals | NOAA Article Title: Search Chemicals Author: NOAA Office of Response and Restoration, US GOV
Website Title: American Cancer Society Article Title: What Is Ultraviolet (UV) Radiation? cancer/prevention-and-early-detection/what-is-uv-radiation.html
Website Title: LiveScience Article Title: What Is Ultraviolet Light? Publisher: Purch Electronically Published: September 15, Author: Jim Lucas