It is likely that Atopobium parvulum produces H2S during the fermentation of sulfate-containing compounds27,28,51,85 as suggested by a reduction in carcinogenesis by treatment with bismuth, a H2S scavenger in an IL-10-/- model of CRC.84 Tsoi et al86 demonstrated that ROS and cholesterol produced by Peptostreptococcus anaerobius, which is increased in human colon tumors, enhances AOM-induced tumorigenesis in mice through TLR2/4. The gene discussed is IL10; the disease is colorectal carcinoma.