Expert: Paras Anand - 1/19/2009

Question
My friend and I are doing a science fair project on bacteria in tap water, well
water, ect.  I was wondering how you would test the water with a petri dish.  
would you swab the water and then place it into the dish?  I have been trying to
look up the answer but I can't find it anywhere.

Answer
Hi! Kelsey,

I would suggest that you use a centrifuge. Centrifuge your water sample to pellet the bacteria (2000g for 5min). Discard the upper part that is water. Finally dissolve this pellet in some media (or phosphate buffer saline). And then you can spread this water in different dilutions onto media plates.

Best,