Sourdough controversy: Where do the microflora come from? Are they replaced over time?
The question recently posted about Ed Wood's (www.sourdo.com) starters brought to mind one of the great sourdough controversies: Do the original strains of yeast and lactobacilli in a purchased or gifted starter persist, or are they replaced over time by the yeast and lactobacilli strains native to the locality, or are they replaced by the flora on the flours used to feed the starter?
Ed is adamant about the flora in the starters he sells continuing forever. Others insist on one of the other theories.
Since most of the yeast and lactobacilli in grain supposedly adhere to the outer parts (bran) of the berries, does feeding a starter exclusively with "white" flour help preserve the original flora? Is it necessary to do this to prevent their replacement, or will the original flora continue to dominate in a healthy culture regardless of what kind of flour it is fed?
What do you all think? Does anyone know of data (not anecdotes!) that speak to these issues?