The bacteria called Fusobacterium nucleatum plays an important role in causing gingivitis and periodontal disease. It is also found in the placenta. Gingivitis is an interesting disease, because people who have gingivitis also tend to have higher risk of a number of other problems, such as diabetes and heart disease. It has been a long-running debate whether gingivitis causes these other diseases or whether it’s just a non-causal correlation.

Into that debate drops this bombshell: a paper recently published in Nature just reported that Fusobacterium, which was previously reported to be found in many patients with colon cancer and to induce tumors (in this paper, they show the bacteria recruit immune cells to the tumor, which is very very bad–immune cells often help the tumor cells much more than they harm them, contrary to conventional wisdom), actually travels with the colon cancer cells when the cells metastasize. Yup, you read that right. You can find the bacteria in mets, such as liver mets! Here is a layman’s explanation in the New York Times.

Not only that, but get this. When they made xenografts from those tumors–that is, they took the cancer cells and put them under the skin in immunodeficient mouse, which is a standard technique to study tumors–they found the bacteria in the xenografts! And not only that, in subsequent xenografts made from those xenografts, the bacteria persisted!

And the pièce de résistance? When they treated these mice with antibiotics that killed the bacteria, tumor growth slowed! See the graph below.

They did not this inhibition of growth when they treated the mice with antibiotic that didn’t kill the bacteria, nor did they see this in xenografts that didn’t have the bacteria (from patients whose tumors didn’t have the bacteria).