Christine Tricarico, age 10, of Staten Island, New York, for her question:

What makes those holes in Swiss cheese?

Obviously it is impossible to put those round holes inside a solid slab of Swiss cheese. Nevertheless, there they are  so there must be an explanation. Well, if you must know, they were put there by something that goes by the ridiculous name of Propionibacterium helveticum. If you sift through those letters you will find a group that spells bacterium which is the singular of bacteria. Not all bacteria are enemy germs, remember. And this one happens to be a friendly cheese maker.

The cheese is made from the solid clumps in curdled milk. But human cheese makers cannot possibly change this .poop into tangy tasting Swiss cheese, properly riddled with big empty bubbles. So they add a carefully preferred helping, of that special bacterium and his relatives. He digests the milk solids, which too add that delicious tangy flavor. He also gives off bubbles of gas that get trapped inside the cheese as it ripens and becomes solid. So those holes in Swiss cheese are created by friendly bacteria.