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

7. 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

8. Research S. mutans S. epidermidis
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
S. mutans
S. epidermidis
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.

9. Procedure II Saliva will be extracted
Lysozyme was used as a control; 2 tabs soaked in this
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

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 Improvements
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.
Testing other elements besides saliva.

14. Any questions? Thank you!
National Center for Biotechnology Information. N.p., Oct Web. 30 Nov.       2009. <
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. <       ?cookieSet=1&journalCode=ode>.
Any questions?