[Microbiota and colorectal cancer: genotoxic bacteria in the intestinal tract].

Numerous studies support a role for the intestinal microbiota in colorectal tumorigenesis. Although colon cancer has not yet been epidemiologically linked to specific bacterial species, recent results suggest that certain toxigenic commensal bacteria may be oncogenic Strains of Escherichia coli, a ubiquitous member of the colonic flora, synthesize a genotoxin called colibactin. These bacteria induce DNA double-strand breaks in intestinal cells and trigger chromosomal instability, gene mutations and cell transformation. Thus, long-term colonization of the colon by rogue commensal bacteria capable of causing chronic DNA damage could contribute to the development of sporadic colorectal cancer.