Electron micrograph of bacteria-infecting viruses
Bacteria sometimes commit suicide for the good of the group. When a virus infects a bacterium, the cell kills itself rather than allow the virus to replicate inside it and spread to the surrounding bacteria.
The way this works is that when viruses aren’t around, the bacteria manufacture both a bacterial cyanide pill—a toxin molecule they could use to wipe themselves out if they come under attack—and an antitoxin molecule that keeps the toxin in check. When a virus infects the bacterium, the toxin is released, kills the bacterial cell, and prevents the virus from spreading to other cells. It’s bad for the individual bacterial cell but good for the community—and certainly bad for the infecting virus. Now researchers have found a virus that manipulates this mechanism for its own means, saving itself by keeping its host bacteria from cellular suicide.
This particular virus, called ΦTE, is normally vulnerable to this defense. But researchers have found some mutants of ΦTE that manage to beat the system. These mutants produce their own version of the antitoxin molecule, preventing suicide of the bacterial host. Though other viruses have come up with ways to avoid these bacterial suicide systems, researcher George Salmond says, as far as he knows, this is the first virus to do so by mimicking a bacterium’s antitoxin. By keeping one cell alive, the virus goes on to attack the entire population.
Bacteriophage image via Graham Beards