The Effect of Saliva on Bacteria Mackenzie Abate 9th Grade

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.

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

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

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

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

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

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.

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

Data

Data

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.

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.

Any questions? 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?