Culture inoculated with a sterile loop I had a dog lick. The red broth in the other tube is uninocul
Culture inoculated with a sterile loop I had a dog lick. The red broth in the other tube is uninoculated for comparison. The red is a pH indicator called phenol red that is red at neutral pH, turns yellow in acidic pH and more of a fuschia at basic pH. Bacteria tend to produce acid when digesting sugars, hence the yellow color change. The cloudiness of the broth is also due to bacterial growth. You can’t see it in the picture but there also seem to be “layers” of bacteria, as the species that need oxygen grow towards the top where the air is and the species that die in oxygen grow near the bottom, as far away from the air as possible. This “experiment” was basically just to amuse a kid (and me) -- source link
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