To answer my question: It is undoubtedly,
Saccharomyces cerevisiae. Baker’s yeast is used millions of times daily in making bread and pastries, brewing beer, wine, sake, cider, and hard spirits, just to name a few of its uses.
S. cerevisiae, was the first eukaryote to have its entire genome sequenced in 1996.
Lee Hartwell won the Nobel Prize in Medicine in 2001 for his work on the mitosis genes in S. cerevisiae. It will soon be possible through gene insertion to make the yeast metabolize various chemical constituents and molecules. There you have it.