Closing in on the elusive colibactin toxin

Abstract

More than a decade ago, researchers discovered that bacteria in the human gut have been organizing a mutiny. They produce a toxin capable of damaging our DNA. The team, led by Eric Oswald and Jean-Philippe Nougayrede of Inserm, a French medical research institute, reported that strains of Escherichia coli containing a particular gene cluster could break double-stranded DNA in mammalian cells (Science 2006, DOI: 10.1126/science.1127059). DNA damage is never a good thing, but this toxin has been particularly troubling. The E. coli that produce it are present at high concentrations in the guts of people with colon cancer. And in the lab, these bacteria increase the number of colorectal tumors in mice. So researchers want to isolate the toxin, with hopes of studying it and figuring out its role in cancer. The problem is that the toxin, now dubbed colibactin, is a slippery character—or characters. After the Inserm work, scientists