A question came in regarding a post from yesterday: if the starter recipe is just flour and water, where does the yeast come from? The answer: from the air. Though there’s some laying dormant in the flour, too. And there’s a little in the water…oh, the stuff is everywhere. But the difference between the yeast that’s say, on your eyelashes right now and the yeast that’s in the starter bowl is that the starter yeast is being given everything it needs to grow. Namely water and an abundance of food.
But yeast isn’t all there is to a starter. If it were, it wouldn’t taste any different than commercial yeast out of a packet. A starter is actually a combination of two types of critters: yeast (always some type of Saccharomyces or “sugar fungus”) and lactic acid-producing bacteria. These two forms of life work in a kind of tag-team in a bread starter, the yeast providing the lift and the bacteria providing the flavor.
Many varieties of both can be found in just about every climate on Earth. The possible combinations, and the flavors they produce, are determined by the climate you live in.