Viruses communicate and decide whether to infect or kill their host. The research supporting this statement is the first to have documented viral communication as an organized system through the means of molecular languages.
Should the results of this research be confirmed by follow-up studies, researchers will have a better shot at stopping viral attacks by blocking this communication system.
Viral Communication Discovered
The communication process was discovered by a team of researchers led by microbial geneticist Rotem Sorek at Israel's Weizmann Institute of Science.
The researchers were seeking evidence that a bacterium, Bacillus subtilis, alerts other bacteria to phages. The researchers were aware that bacteria communicate with their brethren through a series of chemicals they secrete and sense, in a process formally called quorum sensing.
The method allows bacteria to alter their behavior depending on the other bacterial formations around them, on their density, and their number. One of the uses of quorum sensing was picking the right time to divide or to infect the host.
While searching for this type of alert, the researchers found something more interesting. They discovered that a viral invader of Bacillus, a phage called phi3T, creates a chemical that affects how other viruses behave.
A bacteriophage is a virus within a bacterium that infects and replicates without leaving its host. Some of these phages can infect cells through two different methods. The first one, and the more common, involves hijacking the host cells, after which the bacteria multiply until the host dies.
The second one, which is less frequent, involves the phages inserting their own genetic signature in the genome of their hosts. After this process they remain dormant until they receive a trigger transmitting that it is safe to start multiplying.
The current research shows the modification in the phi3T's behavior depending on the outputs of the viral communication process. To test this, the researchers injected phi3T into a flask containing Bacillus subtilis bacteria, and discovered that the virus killed it.
Next, the team filtered the contents of the flask to remove bacteria and viruses while keeping tiny proteins. The remaining medium was then introduced to a new culture of bacteria and phages. This process altered the behavior of the phage. Instead of killing the bacteria immediately, the phage became more likely to insert its genome in it.
The researchers believed that a specific molecule is responsible for this process. Calling the molecule "arbitrium," which means "decision" in Latin, they did further studies to identify it.
Arbitrium, Key Protein In Viral Communication
Two and a half years of research later, Sorek and graduate student Zohar Erez found that arbitrium was a protein that slips out of infected bacteria when they die. As the levels of arbitrium increase, phages stop killing the bacteria. Instead, they go to bacterial genomes and stay dormant until a proper moment comes.
"The arbitrium system enables a descendant phage to 'communicate' with its predecessors, that is, to estimate the amount of recent previous infections and hence decide whether to employ the lytic or lysogenic cycle," the researchers noted in their study, which was published in the journal Nature on Jan. 18.
