Please help. 8th grade science fair project research questions - (Jan/06/2011 )

im doing a science fair project and i need help. my topic for my project is Which grows more bacteria: human saliva, cat saliva, or dog saliva. i will be putting auger at the bottom of a peachtree dish and putting the saliva over it. it will stay covered in a warm place. i will test it for about a week or more. if you can tell me anything about the contents in each that would be great! or if you think theres something that i should change then that would also be great.

Hi Nick,

I'm glad to see you are doing a microbiology project Some tips for culturing samples:

1. Use a sterile cotton swab to collect the sample.

2. Practice aseptic technique. Try not to expose the agar to the air while streaking the plate. An easy way to do this is to set the plate on a table, lift the lid with one hand just enough to get the swab inside without touching the outside, and use the other hand to transfer the sample from the swab to the agar.

3. Feed the test subject a treat AFTER collecting the saliva sample.

The types of bacteria in each saliva sample will be a little different. Try looking up the properties of each species' saliva. What is different about each species' behavior? For example, cats are obligate carnivores that require much higher dietary protein than omnivores like dogs and people. The diet, age, and other habits of the test subject will influence the types of bacteria you find.

Could you be more specific about your experimental conditions? Bacteria isolated from living things like body temperature. Is your incubator close to that temp? A little lower is OK, but the bacteria will grow slower. Some may not grow at all. What type of agar will you use? Nutrient agar will support some types of bacteria but not others. Most bacteria isolated from mammals like sheep blood agar. In a research or diagnostic laboratory, we incubate for 24 hr or 2-3 days, depending on what we're culturing and the tests we need to do. In class labs, we would incubate 3 to 4 days.

Also consider sources of contamination for your project. Bacteria from your skin or the air may be transferred to your plate if you aren't careful. You could try a control plate for each to identify potential contaminants for your project. Swab your hand and streak one plate, leave another open to the air for about 10 minutes. Check your plates every day. Mold can grow within a few days and mess up your results.

How do you plan to evaluate your data?

Saliva provides nutrients(or simply: food). Saliva contains proteins and sugars that are possible food sources for bacteria.

thank you i really appreciate it!!
my dad has a chicken egg incubator and i plan to keep them in it.
what temprature do you recommend i keep it at if i plan to test for a week?

Nicky135791 on Sat Jan 8 02:09:43 2011 said:

Ask yourself this: what temperature has your mouth? the mouth of a cat? Of a dog?

And do you take the saliva from your dog/cat, sterilise it and then incubate it after letting it stand in the air? or?

And also: a mouth (the entire body) is nothing more then a entire micro-environment ...

If you want to know whats in the saliva, you need to check up some literature on mouthhygiene ..


PS. 8the grade? How old are you then? I dont know the us system.

okay from my research (which i couldnt find much) i think that i should incubate the samples at 100 degrees fairenheit(not good at spelling)

100 Fahrenheit = 37.78 degrees Celsius, which is nearly a degree C higher than your mouth temperature (which should be 37 = 96 F), but it should be OK for what you are trying to do.

Also - peachtree dish = Petrie dish.

Actually, it's "Petri dish" -- named after its inventor, German bacteriologist Julius Richard Petri. Since it's named after a person, it should be capitalized.

bob1 on Thu Jan 13 02:03:23 2011 said:

(just nitpicking) i believe that's 98.6F.

Sorry, quite right on both counts, both typos... that's what I get for not proof-reading my posts and not being able to touch type.