A Huge Experiment May Have Just Revealed the Secret to Multicellularity
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Scientists believe multicellular organisms evolved from single celled life, but understanding how has been difficult.
To finaly understand the process of evolution into multicellularity, researchers studied thousands of generations of yeast cells bonding together.
Snowflakes of yeast formed in a lab may offer some possibilities worth exploring.
The driving force behind the switch from single-cell organisms into multicellular life offers a confounding mystery that scientists haven't cracked. While some believe it came out of evolutionary necessity, there's been no way to show for certain what caused the evolutionary leap.
A new study aims to change that perspective.
Published in the journal Nature, a research team explored how yeast grows and reproduces, creating snowflakes of yeast that potentially demonstrate how a single-cell organism could patch together with other organisms to stay alive and form a multicellular creation.
"This research provides unique insights into an ongoing evolutionary transition in individuality," the authors write, "showing how simple groups of cells overcome fundamental biophysical limitations through gradual, yet sustained, multicellular evolution."
Georgia Tech professor Will Ratcliff told the New York Times that, through over 3,000 generations of yeast, the growth and evolution was so profound that microscopes were no longer needed to see it.
While the team was seeing snowflake yeast—where the yeast was clumping together to form unique shapes—form within 60 days, the researchers also found something else: the yeast was turning itself multicellular. The study notes how, when the yeast divided, it created branches of cells that were all genetically the same.
While an exciting discovery, the team remained intrigued with the fact that there wasn't massive growth coming with this clumping. All of the snowflake yeast remained relatively the same size and in the same squishy state. So, the team invited in a new variable to the experiment, and started varying the oxygen levels each snowflake received.
Researchers say that the yeast that didn't get fed oxygen ballooned so big that you could see them with the naked eye, producing larger cells with dense branches that turned hard. In fact, these oxygen-deprived snowflakes grew up to 10 times larger and 10-fold more biophysically tough, all while retaining a multicellular life cycle.
Understanding this growth from cells in the potential pursuit of oxygen—the snowflakes with an ample avenue toward oxygen remained un-ballooned and relatively similar in size and makeup—could yield more understanding about how a multicellular organism grows and forms, especially with a non-equitable flow of nutrients coming into a cluster.
And that offers up the next step in research. How do these newly formed multicellular yeast clusters handle continued efforts to grow when fed with nutrients? Understanding the yeast may offer up one more clue in the search to fully understand multicellular evolution.
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