They started to band together, eventually evolving into complex organisms like animals and plants.  

How that leap happened is a mystery that has eluded scientists. But now College of Biological Sciences researchers have coaxed normally solitary baker's yeast cells into reenacting the leap, giving science a way to study not only this watershed event but its implications.

For example, the researchers say it's possible that vestiges of the transition to a multicellular lifestyle show up in the way cells age and even how some turn cancerous.

"Because yeast are easy to grow and manipulate, we can investigate a host of important biological and medical topics that are far more difficult in complex multicellular life," says Michael Travisano, an associate professor in the Department of Ecology, Evolution and Behavior (EEB) and senior author of a paper on the work published online in the Proceedings of the National Academy of Sciences.

Scientists have assumed that such a dramatic shift must have taken millions of years. But the CBS researchers evolved new multicellular strains of yeast in just two months.

It all started about two years ago with a casual comment over coffee that bridging the famous multi-cellularity gap would be “just about the coolest thing we could do,” recalls postdoctoral research Will Ratcliff, who is also from the Department of Ecology, Evolution and Behavior.

So they decided to give it a try. Then came the big surprise. It wasn’t actually that difficult. Using yeast cells, culture media and a centrifuge, it only took them one experiment conducted over about 60 days, says Travisano.

Rewards and risks

"In nature, we think multicellularity first evolved as the result of natural selection favoring single-celled organisms that formed clusters," says lead author Ratcliff. "Single-celled predators capable of eating other single-celled organisms, but not clusters, may have inadvertently imposed this selection."

Turning multicellular involves risks, however. For example, a solitary cell that banded together with peer cells would lose autonomy. In particular, cells in the center of a cluster would have less access to resources and fewer opportunities to send out offspring into the world.

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