What is the best way to collect samples to culture on petri dish with agar?

Question

My son is doing a science project to determine which "animal" has the dirtiest mouth. We have sterile cotton swabs to collect the samples. Do we need to put them in a sterile saline solution first, or will the saliva be wet enough to get a good sample? Also, is it best to rub the swab on the agar or roll it on--does it really matter which method is used? Thanks in advance!

Answer 1

I wouldn't put them in saline--salt inhibits some bacteria growth by dehydrating their little insides.

Use a bit of distilled water if you feel the need, but saliva should be wet enough.

I don't guess rub vs. roll makes much difference--just don't rip the petri jell-o stuff.

Answer 2

juz take a spoonful of liquid from the rest room bowl... that's what i did, something comparable, before while my instructor ask us to assemble samples of bacteria from the lake or drain...