All seventeen species were new to science (something that’s pretty typical for microbiome research), so the scientists sequenced their genomes. None of the seventeen species carried genes for toxins or other disease-causing proteins. From an inspection of their DNA, at least, the microbes looked safe.
Next, the scientists tested the bacteria out on mice. They gave the microbes to animals either suffering from colitis or from allergy-triggered diarrhea. In both cases, the bacteria raised the level of Tregs dramatically in the guts of the mice. The mice also partly recovered from their diseases. The mice with colitis had less inflammation, and the mice with diarrhea had healthier stool.