Biology
Culture Media Selection for Bacterial Pathogen Identification
Quick fact
MacConkey agar not only selects for Gram-negative bacteria but also turns pink if the bacterium ferments lactose, instantly distinguishing Escherichia coli from Salmonella.
Why this is interesting
If you take a swab from a sick patient and spread it on a plate of food for bacteria, you'd get a messy mix—yet microbiologists can pick out the villain in a single day. The trick lies in the ingredients they choose.