Virus can eavesdrop on bacterial conversations, study finds

All around us, bacteria are having conversations with one another. And even if we can’t understand the chemical back-and-forth, new research shows that certain viruses, known as phages, can listen in (Cell 2018, DOI: 10.1016/j.cell.2018.10.059).

Bonnie Bassler’s lab at Princeton University studies the ways bacteria communicate. One specific communication tool that her team studies is the quorum-sensing molecule 3,5-dimethylpyrazin-2-ol (DPO). The cholera-causing bacterium Vibrio cholerae pumps out DPO when neighboring cells reach a certain density, or quorum, and a change is needed to survive.

While studying this mechanism, PhD student Justin Silpe searched genetic databases to find other species that can sense DPO. One of his hits was in the tiny genome of a phage. “That was totally surprising,” Silpe says.

Phages are known to detect stress or damage in their bacterial host, and they might also leave messages behind for other phages. But no phages were known to participate in quorum sensing. Silpe found that when phage VP882 senses DPO, its behavior changes: it makes proteins that lead to cell death for the bacteria and escape for the phage.

Bassler’s team “did a marvelous job, and it’s a pretty extraordinary story,” says John Mekalanos, a microbiologist at Harvard University. “It’s really heavy stuff to try and think through and get into the head of a phage. But it’s clearly fascinating.”

Silpe also demonstrated how scientists could engineer VP882 to kill bacteria such as V. cholerae or salmonella on command. But phage therapy will not become a focus for the Bassler lab. The team’s interest is more fundamental. Bassler says she is convinced that these communication strategies are shared across all branches of the tree of life. “It’s time to up the complexity in how we think about quorum sensing and all of its ramifications.”