This event could be at least partly explained by the increased presence of the proinflammatory bacterium Helicobacter, which contributes to exacerbation of enteritis (see above), and the decreased presence of the antiinflammatory bacterium Ruminococcaceae, which prevents colitis and promotes tissue repair (7), in Pla2g2a–/– mice. This evidence concerns the gene PLA2G2A and colitis.