Expansion of Actinobacteria (Eggerthella, Actinomyces), Turicibacter, Streptococcus. Reduced Faecalibacterium. Collinsella correlated with high levels of alpha-aminoadipic acid and asparagine and IL-17A production. Role of Collinsella in altering gut permeability and disease severity confirmed in experimental arthritis. This evidence concerns the gene IL17A and arthritic joint disease.