http://www.labspaces.net/103920/Scie...ctive_behavior

Birds flock. Fish gather in schools. Bees swarm. Even amoebae clump together in mystifyingly clever constellations.

Scientists have long wondered what is happening at the cellular and molecular level to bring about this amazing coordination of so many individual animals, insects and organisms into groups. It's a choreography seen throughout nature from the large-scale to the miniscule, with synchronized movements as precise as the dance lineup of a Broadway musical.

Is there a secret drum major, a leader among the group setting the pace and instigating participation? Or is it that organisms and cells already are moving rhythmically but independently and then find themselves provoked into harmony by an external beat?

A group of scientists seeking the answer to the mystery of collective motion has found strong evidence pointing to a third possibility -- collective behavior can arise in cells that initially may not be moving at all, but are prodded into action by an external agent such as a chemical. Research led by Thomas Gregor, an assistant professor of physics at Princeton, and Satoshi Sawai, a former postdoctoral fellow in the laboratory of Princeton biologist Edward Cox and now at the University of Tokyo, has shown that food-deprived amoebae are prodded into their coordinated clumping by the chemical cyclic adenosine monophosphate (cAMP), effectively changing the parameters of the cell environment.

The chemical is ubiquitous in nature, aiding signaling within living cells and regulating activities like protein production. John Bonner, Princeton's George M. Moffett Professor Emeritus of Biology, put the substance on the map for amoebae in 1967. He showed with his collaborators that certain cells are drawn to cAMP, and provided through a series of experiments one of the clearest demonstrations of chemotaxis -- the movement by a cell or organism toward a chemical stimulus -- ever shown.

"This is the first time in biology that such a mechanism could be shown both at the single cell and at the cell population level simultaneously," said Gregor, the first author on the paper."