Biology subjects

Valence, F.

Publications and source records attributed to Valence, F..

3 recordsLinked to original sources

bioRxiv2024

New insights into the cultivability of human milk microbiota from ingestion to digestion and implications for its immunomodulatory properties

Human milk (HM) microbiota is increasingly studied for its potential health benefits. However, the physiological state of HM bacteria and consequently their effects on gut homeostasis remain a question. This study investigated the physiological state of the HM microbiota by characterizing its cultivable fraction, as it might be at the point of ingestion and assessing the effects of digestion on the cultivability and immunomodulatory properties of six prevalent HM strains. The microbiota of 28 HM samples was analysed by 16S metabarcoding either directly on raw milk (raw milk microbiota, RM) or on the complete cultivable fraction obtained from seven non-selective media (cultivable milk microbiota, CM). Diversity was lower in CM than in RM, with 32 versus 435 genera and a median of 7 versus 69 genera per sample in CM and RM, respectively. CM also showed under-representation of strictly anaerobic genera. Factors like parity and iron or vitamin supplementation affected RM and/or CM. In vitro gastrointestinal digestion moderately impacted strain cultivability. However, most strains partially or completely lost their immunomodulatory properties on the monocyte THP1 cell line after digestion, except a Staphylococcus epidermidis strain that gained immunomodulatory potential.

microbiology↗

bioRxiv2023

Integration of metataxonomic datasets into microbial association networks highlights shared bacterial community dynamics in fermented vegetables

The management of food fermentation is still largely based on empirical knowledge, as the dynamics of microbial communities and the underlying metabolic networks that produce safe and nutritious products remain beyond our understanding. Although these closed ecosystems contain relatively few taxa, they have not yet been thoroughly characterized with respect to how their microbial communities interact and dynamically evolve. However, with the increased availability of metataxonomic datasets on different fermented vegetables, it is now possible to gain a comprehensive understanding of the microbial relationships that structure plant fermentation. In this study, we present a bioinformatics approach that integrates public metataxonomic 16S datasets targeting fermented vegetables. Specifically, we developed a method for exploring, comparing, and combining public 16S datasets in order to perform meta-analyses of microbiota. The workflow includes steps for searching and selecting public time-series datasets and constructing association networks of amplicon sequence variants (ASVs) based on co-abundance metrics. Networks for individual datasets are then integrated into a core network of significant associations. Microbial communities are identified based on the comparison and clustering of ASV networks using the "stochastic block model" method. When we applied this method to 10 public datasets (including a total of 931 samples), we found that it was able to shed light on the dynamics of vegetable fermentation by characterizing the processes of community succession among different bacterial assemblages. IMPORTANCEWithin the growing body of research on the bacterial communities involved in the fermentation of vegetables, there is particular interest in discovering the species or consortia that drive different fermentation steps. This integrative analysis demonstrates that the reuse and integration of public microbiome datasets can provide new insights into a little-known biotope. Our most important finding is the recurrent but transient appearance, at the beginning of vegetable fermentation, of ASVs belonging to Enterobacterales and their associations with ASVs belonging to Lactobacillales. These findings could be applied in the design of new fermented products.

bioinformatics↗

bioRxiv2021

Microbial community dispersal in sourdough

Understanding how microbes disperse in ecosystems is critical to understand the dynamics and evolution of microbial communities. However, microbial dispersal is difficult to study because of uncertainty about the vectors that may contribute to their migration. This applies to both microbial communities in natural and human-associated environments. Here, we studied microbial dispersal among French sourdoughs and flours used to make bread. 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 analyzed whether flour is a carrier of sourdough yeast and bacteria and studied whether microbial migration occurs between sourdoughs. The microbial community of a collection of 46 sourdough samples, as well as that of the flour from which each was made, was studied by 16S rDNA and ITS1 metabarcoding. No sourdough yeast species were detected in the flours. Sourdough lactic acid bacteria (LAB) were found in only five flour samples, and they did not have the same amplicon sequence variant (ASV) as found in the corresponding sourdough. The species shared between the sourdough and flour samples are commonly found on plants and are not known to be alive in sourdough. Thus, the flour microorganisms did not appear to grow in the sourdough microbial community. Dispersal between sourdoughs was also studied. Sourdoughs shared no yeast ASV, except in few cases where groups of three to five bakers shared some. These results suggest that there is little migration between sourdoughs, except in a few situations where bakers may exchange sourdough or be vectors of yeast dispersal themselves.

ecology↗