Résumé
Using sourdough bread ecosystems as a model and a participatory research approach, we have analysedhuman impact on the dispersion and selection of lactic acid bacteria and yeasts. In France, microbialdiversity associated with bread-making practises has recently been documented. In order to betterunderstand the origin of the sourdough microbial diversity, we analyzed the effect of (i) terroir (ii) wheatvarieties, (iii) bakers on sourdough microbial taxonomic and functional diversity. Three populations ofold wheat and three varieties of commercial wheat were each grown on three terroirs. For each terroir,grains from the three old populations were mixed and so were grains from the three modern varieties.The flours of the six seeds lots were sent to four different bakers, who initiated and maintained sixsourdoughs for three weeks. The sourdoughs were then analyzed by cultural and non-cultural methods.Total yeast counts varied from 5.6 log10 to 8.49 log10 CFU/g while LAB counts varied from 7 log10 to10.6 log10 CFU/g. By culture-dependent methods, five yeasts species were identified and fifteen acidlactic bacteria species. The composition of the sourdough dominant species varies according to thebakers but does not appear to change according to the origin of the flour. The sourdoughs impact therising of the dough but the rate of total CO2 release depends mainly on the type of wheat varieties. Thenutritional quality of the bread results from the interaction between the sourdough, the type of wheatvarieties and the terroir. Overall, house microbiota appears to be the main factor driving sourdoughecosystem microbial diversity but the origin of wheat also impacts bread quality. Our results highlightthe role of human and socio-cultural practices in maintaining taxonomic and functional diversity ofmicrobial species.