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? • The reason I wanted to do this project was because I wanted another opportunity to work with bacteria. I find it very interesting. 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 • Heterotrophic • Mixed acid fermentation: lactate, succinate, ethanol, carbon dioxide and acetate • Conjugation, transformation and transduction • Gram positive • Facultative anaerobe • Endospore forming • From maltose, glucose and salicin fermentation, acid is made. • Two types of food poisoning

4. S. mutans S. epidermidis Research • Gram positive • Nonmotile • Metabolizes sucrose to lactic acid • 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 • Ferments maltose, not xylose, sucrose or trehelose.

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

6. Research • Amylase • Enzyme • breaks down carbs from polysaccharides to disaccarides • Lysozyme • Enzyme • “lyses” certain bacteria; breaks down cell walls; rinses away energy sources

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

8. Additional Materials Blank disks Plates of agar Innoculating loop Autoclave Matches Incubator Disposable gloves Safety goggles Materials • Bacteria: E. coli, B. cereus, S. mutans and S. epidermidis • Amylase • Lysozyme

9. Procedure • Saliva will be extracted • 2 tabs will be soaked in each saliva type • 2 tabs will be soaked in amylase • 2 tabs will be soaked in water • 2 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

10. Procedure II • Saliva will be extracted • 2 tabs will be soaked in each saliva type • 2 tabs will be soaked in water • 2 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

11. Procedure (cont’d) • I furthered my research and discovered that the enzyme lysozyme is the enzyme in saliva that breaks down bacteria. • 2 tabs will be soaked in water • 2 tabs will remain blank • All four types of bacteria will be plated again using sterile technique. • Plates will be sealed and stored and 37 degrees Celsius • Bacterial growth will be observed over a period of three days • The zone will be measured on the third day

12. Data

13. Data

14. 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 saliva’s inhibitory effect was equivalent to that of water.

15. Conclusion • What went wrong • A fungus grew on a few of the plates. It possibly came from the air or careless sterile technique. • Improvements • More careful with sterile technique, the bacteria and tabs.

16. 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?