Résumé
Plant and animal domestication has been accompanied by microbial species domestication for fermented food processing. Although industrialization led to the selection and spread of specific fermenting microbial strains, there are still ongoing artisanal processes that may allow the conservation of a wider diversity of microbial species. We examined whether and how the diversity of artisanal practices could lead to an increased level in microbial species diversity for sourdough bread making. Sourdough consists of a mixture of flour and water that is naturally fermented by yeasts and lactic acid bacteria. We analyzed the microbiota of a collection of French sourdoughs and investigated bread making practices. We found that the rupture of the dominant way of producing bread, lead to a higher diversity of bread-making practices which are beneficial for the conservation of yeasts species diversity. We then realized an experiment of domestication in action where farmers grew wheat landraces and modern varieties, and bakers made flours, initiated new sourdoughs and propagated them by adding flour and water, a process called backslopping. We showed that the dynamic of the sourdough microbiota over backsloppings results from the interplay of human mediated microbial dispersion and selection. The local environment, i.e. the “house microbiota”, is the main drivers of the sourdough microbiota. Selection, through the use of different wheat varieties but also different baker’s practices, also appears to drive the divergence of sourdough microbiota. Overall, our results highlight the role of artisanal diversity in the dynamic and conservation of microbial diversity.