Biology/science experiment
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Hi Mr. Hintz,
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My daughter, Rebecca, and I asked you a couple of weeks ago about a science experiment she is doing testing the Five Second Rule. She repeated the portion of the experiment with the homemade bacteria food but did not put the petri dishes in our incubator. This time they did not liquify. (Hooray!) And we did see some bacteria (we think) growth. It was slower and less dramatic than what occurred with Agar and the incubator - but it was growth nonetheless. So we hope you can take a stab at two things we saw occur in this part of the experiment.
As I said, our growth was slower - but in two of the petri dishes it looked almost like a spray across the dish (a sort of splatter pattern in a swath across the surface.) Creamy white in color - but in her other portion of the experiment the growth would cover the surface almost like a wave. IN these dishes it spread in almost individual little dots. Any ideas?
And now for the coolest! Rebecca took pictures and began recording results - and then we got around to cleaning and disinfecting the petri dishes and one of them had a large (quarter sized) red growth that looked almost like a miniature sea fan coral. It was a deep red and looked very different from the mold that had begun to grow in almost all of the dishes (that was white and fuzzy). Of course, Rebecca is sure this is some MAJOR scientific breakthrough - and I told her I would ask you if you had any guesses. Any experiment that generates this much excitement for a 7th grader must be a success! Thanks for your help! Julianne Russell
Hi Julianne
I am glad the study was a success. In the photo you sent the red blotch is a red mold. I also notes a little penicillium mold at the bottom. Keep in mind taht you cannot be sure of bacteria without staining them and looking with a microscope. The white colonies are bacteria or yeasts and are not unusual. I think that these were contaminants that got onto your media before you exposed it because the red mold is growing in the media and not on the surface.
In your other plates the spray pattern were most likely individual colonies of common bacteria probably Staph epidermidis (not the bad staph)
Please tell Rebecca that she may not have made a great discovery but that she did a great job
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Answers by Expert:
Walter Hintz
Expertise
Science teacher for over 50 years. MSc. in biology. I can answer questions in general biology, zoology, botany, anatomy and physiology and biochemistry.
Experience
I have a MSc in biology and have been a science teacher for over 50 years. At present I am a faculty member at a college and a science consultant at seven catholic schools.
Publications
The Ohio journal of Science
Momentum-The Journal of the Catholic Education Association
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