Germ theory of disease and truck: what they have in common

1. Step 1. Germ theory of disease — uses — Culture medium (agar). Koch’s postulates.
2. Step 2. Culture medium (agar) — is used in — Sewage treatment plant. Waste water is cleaned by activated sludge — bacteria.
3. Step 3. Sewage treatment plant — has part — Compressor. Blowers supply oxygen to the microbes.
4. Step 4. Compressor — is part of — Air brake. A compressor pumps the air.
5. Step 5. Air brake — is part of — Truck. Air brakes, as on trains.

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