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Genetic Pickup: Did animals get brain genes from bacteria?

Reviving a controversy about whether animals have acquired key genes from bacteria, a study suggests that microbes have provided genes that now play vital roles in brain-cell signaling and other forms of cell-to-cell communication. The genes implicated encode enzymes required for the metabolism and synthesis of crucial brain chemicals, including dopamine, serotonin, melatonin, and histamine.

"These enzymes did not evolve [in animals]. They were picked up, as a shortcut," contends David C. Klein of the National Institute of Child Health and Human Development in Bethesda, Md.

Klein's collaborators on the study, however, made a similar claim several years ago about the transfer of bacterial genes into human DNA. That assertion was strongly refuted, and the new work has quickly drawn pointed remarks from some of the same critics.

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