Researchers from the University of California, San Diego have found a link between childhood exposure to the bacterial toxin colibactin and the development of colorectal cancer in young adults. Colibactin, produced by certain strains of E. coli, can leave genetic mutations in young patients, potentially accelerating the development of cancer decades earlier than expected. The study examined 981 colorectal cancer genomes from patients in 11 countries and found that mutations associated with colibactin were more frequent in tumors of younger patients. The findings suggest that early-life exposure to colibactin-producing E. coli may be a possible explanation for the rising incidence of colorectal cancer among young adults.