Suicide is an evolutionary puzzle. Why should an organism kill itself when it could be having offspring? Now, researchers have shown that in bacteria, suicide can be worthwhile—and has no major downside. Scientists compared two strains of Escherichia coli bacteria, one that self-destructs when infected with a lethal virus and one that doesn’t. An infected bacterium not only dies but also serves as an incubator for some 300 new virus particles, unless it kills itself first. When the researchers seeded a batch of the suicidal bacteria with the virus, the bacteria thrived, they report online today in the Proceedings of the Royal Society B. That’s because infected individuals self-destructed before they could spread the virus to others. A batch of the nonsuicidal bacteria, however, perished when infected. When both kinds of bacteria and the virus were mixed together under varying conditions, the suicidal strain fared better (as seen in the image, showing green colonies of the suicidal strain to be unscathed, while pink colonies of the nonsuicidal strain have been nibbled away by the virus). That shows there’s no significant cost to suicidal tendencies. After all, infected bacteria are too feeble to reproduce, the researchers point out. So for these microbes, at least, the old song is right: Suicide is painless, as well as a blessing to one’s neighbors.
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