We also found the expression of PLA2G4A, a host gene that plays an important role in arachidonic acid metabolism and modulates gut epithelial homoeostasis70, to be positively correlated with the abundance of Bacteroides massiliensis in IBS, B. massiliensis being known to be prevalent in patients with gut malignancies41 (Fig. 3e). This evidence concerns the gene PLA2G4A and irritable bowel syndrome.