Just chiming in - we use sourdough and no commercial yeast for all of our breads and even pizza dough. I ordered my starter from Sourdoughs INternational,
http://www.sourdo.com/
This sourdough "experiment" was part of my herbalist education, and I got addicted and use it exclusively.
The gluten is "digested" somewhat by the fermentation and that is why sometimes people with gluten sensitivity can eat sourdough bread - real sourdough, not commercial, which loaves often have baker's yeast in them as well as the sourdough leaven.