Bacillus mycoides: zone of inhibition

This is a bit of fun I did with my children to show them the dangers of eating too many sweets. Bacteria are commonly used as poweful sensors for toxins and environmental pollutants so for this experiment I fed some Gummy Bear sweets to the spreading soil bacterium Bacillus mycoides. As you can see from the images above, it doesn’t have many problems with the orange sweet but it seems to find the green sweet very unpalatable and actively avoids it. The zone of no growth around the green sweet is called a zone of inhibition, and a similar method is routinely used to test the effectiveness of antibiotics against bacteria. Here the sweet would be replaced by a paper disc loaded with the antibiotic of interest.

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