Transcript The Effect of Saliva on Bacteria

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.
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E. coli
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Gram negative
Motile
Facultative anaerobe
Mixed acid
fermentation: lactate,
succinate, ethanol,
carbon dioxide and
acetate
Conjugation,
transformation and
transduction
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B. cereus
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Gram positive
Facultative anaerobe
Endospore forming
From maltose, glucose
and salicin
fermentation, acid is
made.
Two types of food
poisoning
 S.
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mutans
Gram positive
Nonmotile
Metabolizes sucrose to
lactic acid
Beta-hemolytic
Allowed to grip to
teeth because of
receptors
Found mainly on teeth
 S.
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epidermidis
Gram positive
Nonmotile
Facultative anaerobe
Grows on plastic
objects in body
Ferments maltose, not
xylose, sucrose or
trehelose.
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Saliva
› 98% water
› Two main enzymes:
 Lysozyme: antibacterial
 Amylase: digestion
› Oral Hygiene: teeth and mouth; residue, particles,
and epithelial tissue.
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Amylase
› Enzyme
› breaks down carbs from polysaccharides to
disaccarides
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If varied types of saliva are used on bacteria,
then human saliva will have the most
inhibitory effect on the bacteria.
Bacteria: E. coli, B.
cereus, S. mutans
and S. epidermidis
 Amylase
 Lysozyme
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Additional Materials
› Blank disks
› Plates of agar
› Innoculating loop
› Autoclave
› Matches
› Incubator
› Tweezers
› Disposable gloves
› Safety goggles
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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
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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
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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
› 2 tabs will be soaked in lysozyme
› 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
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.
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What went wrong
› A fungus grew on a few of the plates. It possibly
came from the air or careless sterile technique.
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Improvements
› More careful with sterile technique, the bacteria
and tabs.
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>.
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