Human research has shown that patients with mutations in Crohn's disease genes such as nucleotide binding oligomerization domain 2 (NOD2) [33] and autophagy related protein 16L-1 (ATG16L1) [34] have decreased numbers of the Firmicutes species of bacteria Faecalibacterium prausnitzii and Roseburia intestinalis in their ileum [35]. The gene discussed is NOD2; the disease is Crohn disease.