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.
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Posted by Dr. Tim Sandle