Just about each and every starter is different from any other one. This is why some starters or sours will sell for as much as $20,000.00. Did you know that Panetone (a type of Italian fruit bread) is traditionally made from a sour? And it goes without saying that San Francisco Sourdough bread is also made from a sour, but with a significantly different resulting flavor profile. True, sours and natural starters are made up of a mix of wild yeasts and an assortment of different types of bacteria. It is the specific strain(s) of each, and the mix of them that is responsible for the performance of the sour or starter. In Mexico a starter is commonly used for some types of breads, and the way they make the starter is to save a quantity of dough, to this they add water and flour to feed / propagate it, then they use a portion of this to culture the new dough. Since the original dough is typically made with baker's yeast as the dominant microflora, if it is properly managed, baker's yeast should remain the dominant strain of microflora, and the flavor profile will not change very much, but occasionally, something goes wrong, the starter is left uncovered, or it is allowed to stand at an incorrect temperature (one that is not conducive to the propagation of the baker's yeast) and the starter is lost, meaning that it either doesn't perform as well as it used to, or it imparts a different, and usually undesirable, flavor to the finished product.
Developing and maintaining a sour or starter is a fun undertaking, and also to some extent, an art form where bread flavors are concerned.
Tom Lehmann/The Dough Doctor