Colibactin

Colibactin is a genotoxic metabolite produced by "Escherichia coli" and other "Enterobacteriaceae" ("enteric bacteria") believed to cause mutations leading to colorectal cancer and the progression of colorectal cancer. Colibactin is a polyketide peptide that can form interstrand crosslinks in DNA. Colibactin is only produced by bacterial strains containing a polyketide synthase genomic island ("pks") or "clb" biosynthetic gene cluster. About 20% of humans are colonized with "E. coli" that harbor the "pks" island.
Colibactin forms DNA inter-strand cross-links by alkylation of adenine residues on opposing DNA strands.