Just to be sure, the water is then treated with iodine. The water on the Station is many times cleaner than what we drink at home. Microbes must also be kept from growing on surfaces of the Station. This is not only for the health of the crew but also to protect the Station's hardware. They'll eat pretty much anything.
Fungi come in a wide variety of sizes and forms.
Yeast, used for baking bread is a tiny, one-celled fungus. Mushrooms are fungi we buy at the supermarket and enjoy in salads and other dishes. They use most materials as a source of food. If you see bathroom tile that's been covered by mold for a long time, you can tell that the mold has eaten into the tile and grout. As shown by the well-know problems with mold and other fungi aboard the Russian space station Mir, microbes can thrive in the metallic world of a space station.