Viruses communicate for decision-making

Bacteria secrete signalling molecules that allow them to perceive their population density and change their behaviour accordingly. In an exciting turn of events, while searching for bacterial communication systems, Rotem Sorek and colleagues found that some phages—viruses that infect bacteria—encode peptides that are secreted from infected cells and sensed by the viral population. Beyond a certain threshold, the viruses switch from employing the lytic cycle, in which they kill the host cell, to the lysogenic cycle, in which they avoid killing off their hosts. This is the first viral communication system to have been described.