19 October 2010

The closer you look, the more there is to see: Bacteria are talking to each other and they may be thinking, too. Inside our bodies.

Some 100,000 Myxococcus xanthus cells amassed into a fruiting body with spores, above. Experimental competitions showed that some strains of this social bacterium exploited others

Bacteria use chemicals to talk to each other and to nonbacterial cells as well. These exchanges work much as human language does, says Herbert Levine of the University of California, San Diego’s Center for Theoretical Biological Physics. With colleagues from Tel Aviv University, Levine proposed in the August 2004 Trends in Microbiology that bacteria “maintain linguistic communication,” enabling them to engage in intentional behavior both singly and in groups. In other words, they have “social intelligence.”

…Researchers have found several reasons to believe that bacteria affect the mental health of humans. For one thing, bacteria produce some of the same types of neurotransmitters that regulate the function of the human brain. The human intestine contains a network of neurons, and the gut network routinely communicates with the brain. Gut bacteria affect that communication. “The bugs are talking to each other, and they’re talking to their host, and their host talks back,” Young says. The phrase “gut feeling” is probably, literally true.…

…Giovannoni stops short of claiming that bacteria are actually thinking. But the litany of bacterial talents does nibble at conventional assumptions about thinking: Bacteria can distinguish “self” from “other,” and between their relatives and strangers; they can sense how big a space they’re in; they can move as a unit; they can produce a wide variety of signaling compounds, including at least one human neurotransmitter; they can also engage in numerous mutually beneficial relationships with their host’s cells. Even more impressive, some bacteria, such as Myxococcus xanthus, practice predation in packs, swarming as a group over prey microbes such as E. coli and dissolving their cell walls.…

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