Microbial community dispersal from wheat grains to sourdoughs: A contribution of participatory research

Abstract

Understanding microbial dispersal is critical to understand the dynamics and evolution of microbial communities. However, microbial dispersal is difficult to study because of uncertainty about their vectors of migration. This applies to both microbial communities in natural and human‐associated environments. Here, we studied microbial dispersal along the sourdoughs bread‐making chain using a participatory research approach. Sourdough is a naturally fermented mixture of flour and water. It hosts a community of bacteria and yeasts whose origins are only partially known. We analysed the potential of wheat grains and flour to serve as an inoculum for sourdough microbial communities using 16S rDNA and ITS1 metabarcoding. First, in an experiment involving farmers, a miller and bakers, we followed the microbiota from grains to newly initiated and propagated sourdoughs. Second, we compared the microbiota of 46 sourdough samples collected everywhere in France, and of the flour used for their back‐slopping. The core microbiota detected on the seeds, in the flour and in the sourdough was composed mainly of microbes known to be associated with plants and not living in sourdoughs. No sourdough yeast species were detected on grains and flours. Sourdough lactic acid bacteria were rarely found in flour. When they were, they did not have the same amplicon sequence variant (ASV) as found in the corresponding sourdough. However, the low sequencing depth for bacteria in flour did not allow us to draw definitive conclusion. Thus, our results showed that sourdough yeasts did not come from flour, and suggest that neither do sourdough LAB.

Preservation characteristics and bacterial communities of crimped ensiled barley grains modulated by moisture content and additive application

“…On the other hand, Pseudomonas was found in negligible quantity in samples produced with medium and high MC. Von Gastrow et al (2022) , similarly to our study, found that wheat grains shortly after harvest also had ample relative abundance of Pseudomonas , Erwinia , Massilia , Paenibacillus and Sphingomonas . Again, the different additives, except LAB at medium and high MC, had the same pattern regarding the relative abundance of genera communities within each MC level and no distinguished differences were observed between additives.…”

“…and Pseudomonadaceae. In concordance with the results of Von Gastrow et al (2022), Lactobacillaceae was also not found in recently harvested wheat grain, but it was widely present in other stages of the production chain. The different additives had the same pattern regarding the relative abundance of communities within each MC level and no noticeable difference was observed between additives.…”

Domestication of different varieties in the cheese-making fungusGeotrichum candidum

“…small terminal clusters in the tree with no branch length). These clonal lineages have each been isolated from different cheese types and different French regions, indicating asexual multiplication due to strain culture and commercialization, and migration between cheese makers 76 . The existence of admixed commercial starter strains, belonging to clonal lineages, suggests that admixed lineages have been selected for beneficial traits for cheese making.…”

“…We did not detect in the present study any specific trait in the Cheese_1 population compared to the Cheese_3 population, but our experiments did not capture all aspects of cheese-making; in particular, a feature of goat cheeses caused by G. candidum that could be investigated is their convoluted aspect. Alternatively, the clustering of soft goat cheese strains may be due to migration by strain sharing among cheese makers with similar products, as shown for example in bread yeasts 76 . The cheese populations each had twice as low genetic diversity as the wild population, suggesting bottlenecks due to human selection.…”

Evolutionary ecology of human‐associated microbes

“…Identifying the origins of microorganisms in such communities is often challenging. von Gastrow et al (2023) studied the microbial communities in sourdough, a naturally fermented mixture of flour and water for making bread. They used a combination of lab experiments, metabarcoding and participatory research approaches to understand the origin of the microorganisms in sourdough.…”