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Can dog drool kill saliva?

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by

Sarah Sandoval

on 14 May 2015

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Transcript of Can dog drool kill saliva?

Observations
After 12 Hours:
In the first 12 hours of the bacteria being killed, nothing really happened which supported my hypothesis.
After 24 Hours:
Throughout 24 hours of the experimental process there still wasn't very much happening with the dog saliva and bacteria, except that there was more bacteria growing than being killed.
After 36 Hours:
At the 36 hour mark some things became very unusual. This unusual thing was that a very large amount of bacteria kept growing in all of the petri dishes except Samples B and C.
After 48 Hours:
In the last hours of my experiment i realized that all of the petri dishes with bacteria grew a lot more bacteria. The only ones with the same amount of bacteria from the beginning were Samples B and C. I believe that this is because they were the only ones i didn't add bacteria to.
Information
*Why do dogs drool so much?
-Glands in the dogs mouth produce saliva, which is an enzyme-rich liquid.
*Can dog saliva kill bacteria?
-Dog saliva contains lysozome, an enzyme that destroys harmful bacteria.
*What is bacteria?
-Bacteria are tiny single-celled microorganisms. They are found everywhere.
*What is saliva?
-Watery liquid secreted into the mouth by glands allowing you to chew and swallow.
*Are dogs mouth's really cleaner than humans?
-Humans clean their mouths at least twice a day, while dogs rarely get their mouths cleaned and eat bacteria filled waste.

Facts about Bacteria:
-There's more bacteria in your mouth than there are people in the world.
-The smell of rain is caused by bacteria called mycetes.
-A clean mouth has between 1,000-100,000 bacteria on each tooth.
Purpose:
The main purpose of my experiment is to see if dog saliva will be able to kill bacteria.
Procedures:
1. Open one Petri dish and inoculate it with a few grains of the freeze-dried staphylococcus epidermis bacteria placed in different areas of the Petri dish. Pay close attention to exactly how much of the bacteria you use. Be careful not to use too much. Label this Petri dish as a control #1 and set it aside.
2. Open a second Petri dish and inoculate it with a ¼ teaspoon of dog saliva. Close the dish and label it as control #2.
3. Open a third Petri dish. Inoculate it with exactly the same amount of staphylococcus epidermis bacteria that you used in step #1. Follow this by topping the bacteria with a small amount of dog saliva. Cover the dish and label it as sample A.
4. Pet your cat or dog. Run your hands through your hair. Rub your hands on the grass outside. In short, do something to expose your hands to germs. Carefully open one of the Petri dishes, and hold your hand flat against the agar for a few seconds. Cover the dish and label it Sample B.
5. Repeat step #4. However, before closing the dish, add dog saliva to the areas you touched. Close the Petri dish, and label it with a permanent marker as Sample C.
6. Carefully put all the Petri dishes in an area where they will not be disturbed.
7. Inspect your dishes at 12, 24, 36, and 48 hours. Compare Control #1 to Sample A. Are there more cultures growing in the dish that was inoculated with dog saliva? Compare Sample B to Sample C. Are there more cultures growing out in the dish that you touched or the dish that was touched and treated with dog saliva? Lastly, consider the number of cultures that grew out in Control #2. Can you draw any conclusions on the cleanliness of dog saliva?

Hypothesis:
If there are substances in saliva that can kill bacteria then that would make it easier to kill bacteria.
Can dog drool kill saliva?
Results:
The saliva of animals contains many agents that kill germs and help heal wounds. A few of these agents include:

The enzyme lysine, which breaks the chemical bonds in bacterial cell walls.
The antibody IgA (immunological A), which directly attacks bacteria.
Peroxidase, which help plants defend against bacteria.
Endorphin, which has an analgesic (pain killing) effect.

Other possible agents in saliva that aid the healing process include nerve growth factors (not found in humans, but present in mice), epidermal growth factor, hyaluronan, and others.

Given all these factors, it is not surprising that saliva can exert a healing effect. Students should be able to observe that fewer cultures grow out in both of the dishes inoculated with dog saliva. If students don’t obtain the expected result, help them think through an explanation. Did the dog eat just before the drool was obtained?

Consider other factors such as the mechanical effect of licking. While there is not an effective way of stimulating this in a Petri dish, licking may clean an injured area and remove germs.
Question:
Is dog saliva capable of killing bacteria?
Materials:
5 Petri Dishes that contain sterile agar
Fresh dog saliva from one dog
1/4 tsp.
Freeze-dried staphylococcus epidermis bacteria (non-pathogenic)
Sharpie
Conclusions:
I have concluded that after conducting my experiment I found out that my hypothesis was incorrect. The reasons for this are that instead of the bacteria getting killed by the dog saliva, more grew instead.
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