Posts Tagged ‘quick and dirty’

A quick and dirty microbiology attempt

July 3, 2012

I recently felt compelled to do some microbiology work.  My goal was to make a crude growth media for microorganisms, swab my mouth for these buggers, and spell my name across a few petri dishes.

edit:  Forgive the bright spot from my lamp, it was the only way to get the letters to show.


Above you can see the letter “J”.  If you look to the right and bottom of the J you can see clumpy looking gunk – that is egg chunks.

I started out by boiling 300 g of sliced potatoes and 1 raw egg  in ~500 mL distilled water for 30 minutes.  Next I filtered the solution through numerous coffee filters and then filtered the solution a second time through a 0.45 micron membrane.  10 g of sucrose and 10 g of agar-agar (hardening agent) were added and stirred for ~10 minutes.  Next I sterilized the media and some glass petri dishes (~$1.50 per dish) in a pressure cooker for 25 minutes at 15 psi.  After sterilization I poured the media into the dishes and allowed them to cool and harden.

My open dishes

My open dishes

After I finished sterilizing the media I noticed the solution had clumpy-chunky junk floating all about.  I assume this was leftover egg that got through the filters, though it could also have been impurities from the agar-agar (least likely of the two).

I used a cotton swab to collect bacteria from my teeth and gums and I spelled my name (a letter per dish) across the plates using the swab.  On one plate I put nothing and on the last plate I spit into it to cover the whole thing.



I was happy to see that everything worked perfectly.  The dish with no bacterial additions had no growth.  The dish I spit into had growth all over and the dishes I wrote letters on only grew in the shape of the letter itself!0



Unfortunately condensation leaked all over the plates when I flipped them and blocked some letters from being photographed.

For future experiments I bought a “fitness multivitamin” that contains all of the amino acids and I am going to try and use it as an egg/tryptone/peptone replacement.