Molds are microscopic organisms that tend to be airborne and thus are virtually everywhere. (That’s why not eating room-temperature bread, for example, in a timely manner results in mold growing on it.) Their function is to recycle organic matter, all of which is supposed to be returned to nature for re-use.
The reason people find mold on faucets, shower heads, drains, and toilets—which are wet or damp most of the time—is because organic matter (especially skin cells that are discarded in huge numbers every day) has been deposited naturally on these fixtures. Regularly cleaning them will remove the organic debris and thus prevent mold from growing. It requires an organic, damp substrate for nourishment; it can’t grow on bare metal or other surfaces.
Marlene A. Condon