In 1997 we acquired the authentic San Francisco culture with the wild yeast now classified as Candida humilis and with the bacteria classified as Lactobacillus sanfrancisco. We guarantee this culture contains these organisms as the dominate organisms of the culture. The two organisms have a symbiotic relationship that has helped them survive for over a century. The Lactobacilli require maltose, a nutrient in the flour, for growth. The wild yeast doesn’t use it so together they thrive very well. By comparison most commercial yeasts do utilize maltose and thus are in direct competition with the lactobacilli which is another good reason not to use commercial yeasts.