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Like American soldiers on the shores of Normandy during World War II, salmonella bacteria sacrifice themselves for the greater good -- a phenomenon that may illuminate the evolution of altruism.
When salmonella enter the digestive tract, they fare poorly: other bacteria have already established their positions. But by sending an advance group digging into intestinal tissues, they set off an inflammatory reaction in their host, sweeping away the other bacteria. The advance group also dies, but the intestine is wide-open for colonization by their brethren.
Since the bugs are genetically identical, the trigger is molecular rather than genetic: about one in six salmonella microbes are randomly "selected" during cell division to go kamikaze. (Were the triggers purely genetic, all the bacteria would sacrifice themselves.) The population flourishes because of the selflessness of a few.
The findings, published this week in Nature, dovetail with theories on human altruism; it could also help scientists design treatments for salmonella.
Self-destructive cooperation mediated by phenotypic noise [Nature]
See Also:
- The Early Science of Altruism
- The Future Science of Altruism
- Thoughts on Ants, Altruism and the Future of Humanity
- An Evolutionary Explanation for Altruism
- Honeybee Weapon in War on Cancer
Image: Bärbel Stecher / Wolf-Dietrich Hardt / ETH Zürich
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