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.
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.
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.