How did these communities come about? Was it something dietary that nourished inflammatory species? Antibiotics that killed off the anti-inflammatory ones? Genetic variants that altered the host’s immune system, disrupting its ability to manage its microbes? The last of these seems possible: Wendy Garrett has shown that mutant mice which lack important immune genes end up with unusual communities of gut microbes, and those communities can trigger signs of IBD when transplanted into healthy mice.
