Colibactin, produced via the pks locus in some Escherichia coli and other Enterobacteriaceae, exemplifies the potential of microbiota to directly promote oncogenesis (Nougayrede et al., 2006; Putze et al., 2009): it causes double stranded DNA damage and thereby facilitates tumorigenesis in colorectal cancer (Guerra et al., 2011; Garrett, 2015). The gene discussed is ARAF; the disease is colorectal cancer.