Tiny Acts of Microbe Justice Help Reveal How Nature Fights Freeloaders

http://www.sciencedaily.com/releases/2014/01/140106133245.htm

Jan. 6, 2014 — The idea of everyone in a community pitching in is so universal that even bacteria have a system to prevent the layabouts of their kind from enjoying the fruit of others' hard work, Princeton University researchers have discovered.

Groups of the bacteria Vibrio cholerae deny loafers their unjust desserts by keeping the food generated by the community's productive members away from V. cholerae that attempt to live on others' leftover nutrients, the researchers report in the journal Current Biology. The researchers found that individual bacteria produce a thick coating around themselves to prevent nutrients from drifting over to the undeserving. Alternatively, the natural flow of fluids over the surface of bacterial communities can wash away excess food before the freeloaders can indulge.

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The Princeton findings also provide insight into how all microbes potentially preserve themselves by imposing fairness and resolving the "public goods dilemma," in which a group must work together while also avoiding exploitation by their self-serving individuals, said co-lead author Carey Nadell, a postdoctoral research associate in Bassler's lab.

"The public goods dilemma is a central problem in the history of life on Earth, during which single cells have emerged as collectives of genes, multicellular organisms have emerged as collectives of cells, and societies have emerged as collectives of multicellular organisms," Nadell said.

"At each of these transitions in complexity there has been -- and remains -- the threat of exploitation by single members pursuing their own interests at the expense of the collective as a whole," Nadell said. "Clarifying how exploitation can be averted is therefore critical to understanding how life has taken the various forms that exist today."

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"If V. cholerae's system of extracellular digestion were compromised by exploitation," Nadell said, "the world's supply of carbon and nitrogen would become sequestered on a rapid geological timescale."