Friday, May 13, 2011


We all did a very cool experiment this month. We had to boil and make our own agar, the medium for bacteria to grow on. I think making it ourselves upped the awesome factor a little bit.
Well, when was the last time YOU made your own petri dish media...
 Then we filled our two empty petri dishes. We had to be so patient for a half hour while things cooled.
It was kind of hard. Things take so much longer when you stare at them..
We drew a line down the back of one petri dish dividing into two equal halves, the line was visible through the agar. Marlin collected germs from her keyboard using a piece of scotch tape.

Then we applied the germs to the agar by laying the scotch tape on it a few times.

Then Kaya applied neosporin, a common household triple antibiotic ointment to the half labeled A, and left half B untreated.

We capped the petri dish, taped the lid shut, put it in a ziplock in a drawer out of the sun.
For our next experiment on petri dish number two, we decided to see once and for all if a dogs mouth is cleaner than a humans!  We did the same thing as before, splitting the petri dish in half. Clearly labeled human side, and Dog side. Now the fun part!
Ev collected from Kaya,

and put it on the human side.

Marlin collected a specimen from Zoey,

and put it on the dog side of the petri dish.
It took nearly 10 days for us to see some definite growth.
The results are in!
Yes! Neosporin is an effective antibacterial ointment!

And drum roll please.....
A humans mouth proved cleaner than that of the dog, at the time of culture.

Kaya may have brushed his teeth well that day, OR the dog could have eaten a dead rotting chicken? One may never truly know..
This was a really fun experiment that was mailed to us in our monthly subscription of the young scientist club.
We love these kits!


Jessica said...

That is the coolest! Grace and I did that at our UCONN class but i never would have thought of doing it at home! I have petri dishes and I am going learn how to do this at home so Lilah can try it!


Stephanie said...

Jeez - I've prepped dishes that we've never done anything with TWICE!
Left 'em in the fridge so long that I had to peel out the agar and redo them. hmmph.
I"m interested to see if my homemade cleaners are effective against the eew. I'll bet they are!!
I really should try again, soon.
Nive investigations!!