Photo Credit: Microbe World
Moms sometimes bring work home with them and microbiologist Tasha Sturm of Cabrillo College recently brought home a petri dish as a mini experiment. She took her eight-year-old son’s hand and placed it into the dish. Next she let it incubate for 48 hours and then photographed it yet a few days later.
What she found was normal flora on the hand like Staph., Micrococcus, etc. but as the flora continued to grow (slowly), yeast/fungi started to grow and helped bacteria like Serratia turn red.
"At the end of the experiment she had a small 'Biohaz' which needed to be disposed of properly."
On the science website Microbe World, Sturm explained her process:
"I used a large Kirby Bauer plate (15 x 150 mm) with TSA… Tryptic Soy Agar (TSA) can be purchased through a number of companies (Fisher Scientific, Hardy Diagnostics, Neogen). Most sell it in the powdered form, add water, autoclave, cool to about 55 degrees then pour into the plate, cover with the lid then let solidify. Once the plates are cool then place the hand on the plate making sure to gently pressing the fingers/palm to make contact with the agar. Cover the plate with the lid and place in a 37 degree C incubator for 24-48 hrs… incubate agar side up.
This will grow the normal flora on the hand like Staph.,Micrococcus, etc. Take the plate out and let it incubate/set out with the lid on at room temp (22 degrees C) for several days (3+ days). Normal flora will continue to grow (slowly) and yeast/fungi will start to grow…. usually colored colonies (red/pink/yellow). It will also help bacteria like Serratia turn red. Once grown the plate should be treated as a Biohaz and disposed of properly. The plate should not be opened if mold/fungi is present without proper respiratory protection."