Tuesday, 28 February 2017

How viruses communicate

Viruses have been found to communicate with one another, leaving short “posts” for kin and descendants. The messages help the viruses reading them decide how to proceed with the process of infection, according to research.

Many viruses face a choice after they have infected their hosts: to replicate quickly, killing the cell in the process, or to become dormant and lie in wait. HIV, herpes, and a number of other human viruses behave this way and, in fact, even the viruses that attack bacteria -- phages -- face similar decisions when invading a cell. What causes a virus to choose dormancy over immediate gratification? Prof. Rotem Sorek and his group in the Weizmann Institute's Department of Molecular Genetics have now discovered that, during infection, viruses secrete small molecules into their environment that other viruses can pick up and "read." In this way, they can actually coordinate their attack, turning simple messages into a fairly sophisticated strategy.

Prof. Sorek says that he and his group discovered the communications between phages almost by accident. "We were looking for communication between bacteria infected by phages, but we realized that the small molecules we were finding had been sent by the phages themselves," he says.

To find evidence for this communication, the team grew bacteria in culture and infected them with phages; they then filtered the bacteria and phages out of the culture, leaving only the smallest molecules that had been released to the medium. When they grew more bacteria on the filtered medium, infecting them with the same phages, they were surprised to find that the new phages became dormant rather than killing the bacteria.

Prof. Sorek and his group, led by research student Zohar Erez, along with staff scientist Dr. Gil Amitai and Dr. Ida Levy of the Israel Institute for Biological Research, worked to isolate the communication molecule, eventually discovering that it is a small piece of protein called a peptide; they also worked to identify the gene encoding it and to unravel the way it functions. They found that in the presence of high concentrations of this peptide, phages choose the dormancy strategy, so they named it arbitrium, the Latin word for decision.


Zohar Erez, Ida Steinberger-Levy, Maya Shamir, Shany Doron, Avigail Stokar-Avihail, Yoav Peleg, Sarah Melamed, Azita Leavitt, Alon Savidor, Shira Albeck, Gil Amitai, Rotem Sorek. Communication between viruses guides lysis–lysogeny decisions. Nature, 2017; DOI:10.1038/nature21049

Posted by Dr. Tim Sandle