Evidence is mounting that some bowel cancers are caused by bacteria. One microbe seems to trigger a distinct type of mutation in our DNA, which can be seen in up to one in 10 cases of colon cancer.
“It’s the first bacteria ever shown to change DNA and be carcinogenic,” says Hans Clevers of the Hubrecht Institute in Utrecht, the Netherlands.
Colon cancers are usually seen as stemming from random genetic mutations, with smoking and an unhealthy diet raising our risk. But more recently, suspicions have grown about certain gut bacteria, including a strain of E. coli that produces a substance that can damage our DNA.
This strain, called pks+ E. coli, is more common in the faeces of people who have had colon cancer, but it is unclear if it directly causes the tumours or just grows better in the guts of people who had already developed cancer.