Abstract
There are two primary ways of making bread, either using commercial yeast or sourdough, a mixture of flour and water naturally fermented by yeasts and bacteria. While commercial yeasts have been consciously selected for bread making and sold all over the world, sourdough microbial communities are propagated by local bakers through the addition of flour and water. Previous studies have shown that bread making practices but not geography affect the composition of sourdough microbiota. However, the dynamic of installation of sourdough microbiota was unknown. Using a participatory research approach, we analyzed the dynamic of microbial communities during the establishment of new sourdoughs in four bakeries. We highlighted a strong parallelism of yeast and bacteria installation, which rapidly reached their carrying capacity. A single yeast species and two bacteria species quickly dominated the community, regardless of the experimental flour. Each bakery was associated with a specific sourdough microbial community. The analysis of the genomic evolution of Saccharomyces cerevisiae diversity over backslopping revealed that the same lineage spray across all experimental sourdoughs within a bakery. All together, these results emphasize the key role of dispersion as a driver of microbial diversity.