Cancer mutations can be caused by common gut bacteria carried by many people. This was demonstrated by researchers from the Hubrecht Institute (KNAW) and Princess Máxima Center in Utrecht, the Netherlands. By exposing cultured human mini-guts to a particular strain of Escherichia coli bacteria, they uncovered that these bacteria induce a unique pattern of mutations in the DNA of human cells. This mutation pattern was also found in the DNA of patients with colon cancer, implying that these mutations were induced by the ‘bad’ bacteria. It is the first time that researchers establish a direct link between the microbes inhabiting our bodies and the genetic alterations that drive cancer development. This finding may pave the way to prevention of colorectal cancer by pursuing the eradication of harmful bacteria. The results of this research were published in Nature on the 27th of February.