The lab of Howard Hughes Medical Institute researcher Emily Balskus has discovered that a molecule called colibactin can awaken dormant killer viruses.

Microbes produce harmful compounds to attack each other in the cramped space of the gut. However, colibactin acts on microbial cells, activating latent and deadly viruses hidden in the genomes of some bacteria.

Scientists have known for years that colibactin can cause damage to human cells. Work by Balskus and many others has shown that the compound damages DNA, which in turn can lead to colorectal cancer. Researchers have determined that colibactin damages DNA by forming incorrect bonds within the double helix.

In the latest experiment, scientists have grown colibactin producers along with bacteria that carry latent viruses. They saw that the number of viral particles increased dramatically, and the growth of many virus-containing bacteria decreased. This led them to believe that the molecule caused a surge of active, cell-killing infections. Thus, DNA damage by colibactin acts as a signal for the awakening of viruses.

Many microbes have been adapted to protect against colibactin. Balskus’ lab has identified a resistance gene encoding a protein that neutralizes this compound in a wide variety of bacteria.

Next, Balskus plans to investigate how the compound changes the microbes in the gut—which ones disappear and which ones thrive after exposure to the compound.

“The key to cancer prevention may be understanding the impact of colibactin on the microbial community and how its production is controlled,” says Emily Balskus.