More than 500 million years ago, single-celled organisms on Earth’s surface began forming multi-cellular clusters that ultimately became plants and animals. Just how that happened is a question that has eluded evolutionary biologists.
Now scientists have replicated that key step in the laboratory using common Brewer’s yeast, a single-celled organism.
The yeast “evolved” into multi-cellular clusters that work together cooperatively, reproduce and adapt to their environment–in essence, they became precursors to life on Earth as it is today. The results are published in this week’s issue of the journal Proceedings of the National Academy of Sciences (PNAS).
“The finding that the division-of-labor evolves so quickly and repeatedly in these ‘snowflake’ clusters is a big surprise,” says George Gilchrist, acting deputy division director of the National Science Foundation’s (NSF) Division of Environmental Biology, which funded the research. “The first step toward multi-cellular complexity seems to be less of an evolutionary hurdle than theory would suggest,” says Gilchrist. “This will stimulate a lot of important research questions.”
It all started 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,” recalled Will Ratcliff and Michael Travisano, scientists at the University of Minnesota (UMN) and authors of the PNAS paper. Other authors of the paper are Ford Denison and Mark Borrello of UMN. Then came the big surprise: it wasn’t that difficult.
Using yeast cells, culture media and a centrifuge, it only took the biologists one experiment conducted over about 60 days. Multi-cellular ‘snowflake’ yeast images with a blue cell-wall stain and red dead-cell stain. Credit: Will Ratcliff and Mike Travisano
“I don’t think anyone had ever tried it before,” says Ratcliff. “There aren’t many scientists doing experimental evolution, and they’re trying to answer questions about evolution, not recreate it.”