Finally, using TR-FRET binding assay and gene expression analysis, we demonstrated that the C18-3OH is an agonist of peroxisome proliferator activated receptor gamma. In culture, Holdemanella biformis produced high concentration of C18-3OH. Microbiota analyses revealed that the concentration of C18-3OH was correlated with an increase in the abundance in Allobaculum, Holdemanella and Parabacteroides. The anti-inflammatory properties of FOS were associated with an increase in colonic C18-3OH concentration. To determine whether other bacteria composing the microbiota are able to produce C18-3OH, we targeted the gut microbiota of mice with prebiotic fructooligosaccharides (FOS). Oral administration of C18-3OH decreased colitis induced by dextran sulfate sodium in mice. Results Among all the LCFAs quantified by mass spectrometry in Escherichia coli Nissle 1917 (EcN), a probiotic used for the treatment of multiple intestinal disorders, the concentration of 3-hydroxyoctadecaenoic acid (C18-3OH) was increased in EcN compared with other E. Correspondence to Dr Nicolas Cenac, UMR1220, IRSD, INSERM, Toulouse, Occitanie, France.8 NeuroMicrobiota, European Associated Laboratory (EAL), INSERM/UCLouvain, Toulouse, Brussels, France, Belgium.7 Service de bactériologie-hygiène, CHU Toulouse, Hôpital Purpan, Toulouse, France.6 Centre for Pathophysiology Toulouse-Purpan (CPTP), INSERM, CNRS, University of Toulouse, Toulouse, France.5 Walloon Excellence in Life Sciences and Biotechnology (WELBIO), Louvain Drug Research Institute, Metabolism and Nutrition Research Group, UCLouvain, Université catholique de Louvain, Brussels, Belgium.

4 Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.3 MetaToulLipidomics Facility, INSERM UMR1048, Toulouse, France.2 Farncombe Family Digestive Health Institute, McMaster University Faculty of Health Sciences, Hamilton, Ontario, Canada.1 IRSD, INSERM, INRA, INP-ENVT, Toulouse University 3 Paul Sabatier, Toulouse, France.

Bioedit alpha consensus symbols colon