Microbial colors!

  • November 9, 2013 · 3:00 PM
  • Ahnon's

Scientists have figured out way to identify microbes by growing them on so-called "chromogenic media", that make them turn different colors on a Petri dish.

We'd love to make a completely food-safe version of this, so we can do Microbiology 101 demos with kids. The idea is to bring in a wide variety of colored foods, use each to color some gelatin or agar gel in a Petri dish, streak a mixture of (friendly) microbes on them, and check for any color changes.

For example, plant pigments such as cabbage juice or turmeric that change color based on acidity would allow you to distinguish between yeast and bacteria that produce acid, versus those that don't. Other plant colors may be degraded by certain bacteria, or concentrated by others. We'll have some colored plants and food dyes to experiment with, but please bring some of your own to experiment with. Got some weird oil-based food dyes? Some spice or edible flower you think we may not have thought of? Bring it!

You'll be part of an international DIYbio experiment, get to play with lots of pretty colors, and learn some basic microbiology techniques along the way!


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  • Patrik

    Here's the list of plates we made:

    #1 Bryce - cabbage + probiotic
    #2 Rebecca - turmeric + probiotic
    #3 Ken - cabbage + kombucha
    #4 Matt - marigolds + kombucha
    #5 Ahnon - Vit B complex + kombucha
    #6 Christopher - turmeric/beet + kombucha
    #7 Fran - cabbage + yeast
    #8a Patrik - all food dyes + kombucha
    #8b Patrik - all food dyes + probiotics
    #9 There is no #9
    #10 Christopher - cabbage/marigold/beet/turmeric + yeast/kombucha/probiotic
    #11 Matt - cabbage/turmeric/alkali + kombucha
    #12 Matt - turmeric/beet + kombucha
    #13 Ahnon - turmeric + yeast
    #14 Patrik - cabbage/marigold +yeast/probiotics/kombucha

    The commercial probiotic mixture we used was "Acidophilus ProBiotic-4" from KAL, inoculated in some warm milk beforehand. According to the label, it's supposed to contain L. acidophilus, L. bulgaricus, S. thermophilus, and B. bifidum.

    November 24, 2013

  • Francis R.

    How did the cultures turn out?

    1 · November 14, 2013

    • Patrik

      And some have that fruity kombucha smell (before the vinegar kicks in...). They're sitting at room temperature, so it'll take a while for colonies to get large enough that we can expect to see color changes in the medium. Putting them in an incubator at 37C would speed up the process, but can also select for pathogens such as E. coli or staph.

      2 · November 14, 2013

    • Ken O.

      worth any photo documentation yet?

      November 14, 2013

  • Rebecca E S.

    I had to leave early because of a social event but was very interesting.

    1 · November 11, 2013

    • Ahnon

      Good to see you Rebecca!

      November 14, 2013

  • Patrik

    Check out the great pics by Ken Osborn on the Photos page: http://www.meetup.com/Counter-Culture-Labs/photos/18472712/ !

    2 · November 11, 2013

  • Patrik

    Lots of fun! And who knows, we might actually get some useful science out of it as well...

    2 · November 9, 2013

  • Ken O.

    fun group - educational and engaging venue

    2 · November 9, 2013

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