The Effect of Saliva on Bacteria

1. The Effect of Saliva on Bacteria Mackenzie Abate 9th Grade

2. Problem/Rationale • Does saliva have an effect on bacteria? • If so, what is this effect? • Also, I have always heard people say “a dog’s mouth is cleaner than a human’s.” By testing the saliva’s effect on bacteria, I tested the cleanliness of the mouth.

3. E. coli B. cereus Research • Gram negative • Motile • Facultative anaerobe • Mixed acid fermentation • Conjugation, transformation and transduction • Gram positive • Facultative anaerobe • Endospore forming • Mixed acid fermentation • Two types of food poisoning

4. Research • Saliva • 98% water • Two main enzymes: • Lysozyme: antibacterial • Amylase: digestion • Oral Hygiene: teeth and mouth; residue, particles, and epithelial tissue.

5. Hypothesis • If varied types of saliva are used on bacteria, then human saliva will have the most inhibitory effect on the bacteria.

6. Additional Materials Blank disks Plates of agar Innoculating loop Autoclave Matches Incubator Tweezers Disposable gloves Safety goggles Materials • Bacteria: E. coli, B. cereus • Amylase

7. Procedure • Saliva will be extracted • 4 tabs will be soaked in each saliva type • 4 tabs will be soaked in amylase • 4 tabs will be soaked in water • 4 tabs will remain blank • The E. coli and B. cereus will be plated using sterile technique • The tabs will then be added to the bacterial plates • The plates will be sealed and stored at 37 degrees Celsius • Bacterial growth will be observed over the period of 3 days • The zone of inhibition will be measured

8. S. mutans S. epidermidis Research • I furthered my research and discovered that the enzyme lysozyme is the enzyme in saliva that breaks down bacteria. • Enzyme • It “lyses” certain bacteria; breaks down cell walls; rinses away energy sources • Gram positive • Nonmotile • Beta-hemolytic • Allowed to grip to teeth because of receptors • Found mainly on teeth Gram positive Nonmotile Facultative anaerobe Grows on plastic objects in body

9. Procedure II • Saliva will be extracted • Lysozyme was used as a control; tabs will be soaked in this • 4 tabs will be soaked in each saliva type • 4 tabs will be soaked in water • 4 tabs will remain blank • The S. mutans and S. epidermidis will be plated using sterile technique • The tabs will then be added to the bacterial plates • The plates will be sealed and stored at 37 degrees Celsius • Bacterial growth will be observed over the period of 3 days • The zone of inhibition will be measured

10. Data

11. Data

12. Conclusion • My hypothesis stated that if three different types of saliva were used to inhibit bacterial growth, then human saliva would be the most effective in doing so. • This hypothesis was not supported by the data because though bacterial growth varied there were no clear zones of inhibition.

13. Conclusion • What went wrong • A fungus grew on a few of the plates. It possibly came from the air or careless sterile technique. • Some tabs were not “soaked” in the saliva. The ones that were soaked were not timed. • Improvements • More careful with sterile technique, the bacteria and tabs. • Testing other elements besides saliva. • Timing the length of time each disk soaked in either its solution or saliva. Some disks were not able to be properly “soaked” due to the method of extracting saliva (?)

14. Thank you! • National Center for Biotechnology Information. N.p., Oct. 1999. Web. 30 Nov.      2009. <http://www.ncbi.nlm.nih.gov/pubmed/10553245>. • Leboffe, Michael J., and Burton E. Pierce. A Photographic Atlas for the Microbiology Laboratory. Englewood: Morton Publishing , n.d. Print. • Sherwood, Lauralee. Human Physiology. N.p.: Thomson, n.d. Print. • Tenovuo‌, Jorma. "Antimicrobial function of human saliva - how important      is it for oral health?" Informahealthcare.com. N.p., n.d. Web. 30 Nov.      2009. <http://informahealthcare.com/doi/abs/10.1080/      000163598428400?cookieSet=1&journalCode=ode>. Any questions?