Biology

Evolution experiment yields yeast 20,000x bigger and 10,000x tougher

View 3 Images
Microscope images of modules of "evolved" yeast with elongated cells, forming larger clusters
Georgia Tech
Microscope images of modules of "evolved" yeast with elongated cells, forming larger clusters
Georgia Tech
Snowflake yeast cells were grown from clusters of about 100 cells (left) to half a million cells (right) through the team's evolution experiment
Georgia Tech
A scanning electron microscope image of the internal structure of the evolved yeast clusters
Georgia Tech
View gallery - 3 images

Scientists are conducting a long-term experiment on evolution in the lab, to investigate how single-celled organisms could evolve into multicellular lifeforms. After thousands of generations, their yeast grew 20,000 times bigger and 10,000 times tougher.

The idea of an evolutionary “missing link” usually conjures images of a hairy ape-like hominid, but there are actually much more profound missing links in the chain. One of the biggest gaps sits between single-celled and multicellular organisms, which marks a key step in the development of complex life on Earth.

Now, scientists from Georgia Tech have reported the first results of an experiment that they hope to continue running for decades, with a pretty lofty goal – evolving single-celled lifeforms into brand new multicellular lifeforms. Directed evolution experiments have been conducted for decades, even winning the Nobel Prize for Chemistry in 2018, but those are usually focused on making new drugs or solving other problems, not plugging holes in our distant family tree.

In this first phase of this Multicellularity Long-Term Evolution Experiment (MuLTEE), the researchers started with a species called snowflake yeast. The microbes were grown in shaking incubators, and every day the team would engage in a spot of artificial natural selection – colonies that had grown the fastest and reached the biggest sizes were selected for further cultivation. Repeat this process thousands of times over, and you’ve got a pretty good approximation of the environmental forces that favor certain characteristics in natural evolution.

And sure enough, after about 3,000 generations, the yeast had evolved to form clusters of more than 500,000 cells – more than 20,000 times larger than the original strain. In the process they’d become visible to the naked eye, and had become around 10,000 times tougher, on par with wood.

Snowflake yeast cells were grown from clusters of about 100 cells (left) to half a million cells (right) through the team's evolution experiment
Georgia Tech

The scientists investigated closer to find out what had happened on the cellular level to grant them such impressive progress. They found that the individual yeast cells had all stretched out, which reduced the density of cells in each group and as such, reduced the stress that they put on each other. This keeps the clusters from fracturing like they normally would at a certain density, allowing them to grow bigger.

But this mechanism alone shouldn’t have resulted in such a dramatic increase, the team says. So they looked even closer, using a scanning electron microscope.

“We discovered that there was a totally new physical mechanism that allowed the groups to grow to this very, very large size,” said Ozan Bozdag, first author of the study. “The branches of the yeast had become entangled – the cluster cells evolved vine-like behavior, wrapping around each other and strengthening the entire structure.”

While the “evolved” yeast still lacks many of the biological features of truly multicellular organisms, this cellular entanglement seems to be a milestone on the road to that end. The experiment is far from over too, so further developments are likely on the way.

The research was published in the journal Nature.

Source: Georgia Tech

View gallery - 3 images
  • Facebook
  • Twitter
  • Flipboard
  • LinkedIn
9 comments
rgbatduke
And what could possibly go wrong?

Don't answer that. Too many things to count. I just hope to hell they are doing this in a clean room environment while wearing space suits. If one day I see clumps of yeast oozing down the street and munching on grass and trees and pets, I'll know I was wrong and who to blame...
Don Rathburn
Fair enough, the yeast has certainly changed. But evolution, I think that is a bit of a stretch. Now if the colony had grown eyes, legs, and a brain, and crawled out of the flask, now THAT would be impressive, for sure.
TechGazer
To Don Rathborn: this is definitely evolution. Evolution is not a force driving an organism towards an end goal of human-like. Evolution is the selection of organisms that survive better in their environment. It doesn't matter that this environment is artificial selection by filters or however they are doing it. Evolution will make organisms simpler if that better suits the environment. Mitochondria are an example of that; the original bacteria lost a lot of DNA, specializing in ATP production while the host cell took over many of the bacteria's earlier internal functions.
KevinG
The real question, is what kind of bread and beer can be made from this super yeast.
Karmudjun
Excellent Article Michael. The researchers at Georgia Tech are NOT allowing for natural selection or evolution - they are manipulating for the hardiest and fastest growing species and just watching what could happen. While some may say "What could possibly go wrong", I say "What could possibly go right?" The hypothesis that continued growth of these colonies will allow mutations and happenstance to achieve multicellular growth. It certainly would parallel the evolution in nature to a degree. Judging from the pictures, this is not conducted in a biohazard protective environment - likely in test tubes in an upper level biology laboratory. Who knows if the modified snowflake yeast cells have a competitive advantage in the real world - the colonies are not exposed to real world pressures. Like Sourdough yeast starters cultivated in wagons and kitchens across the USA, they may exhibit some "wild" characteristics, or they may depend upon humans for continued cultivation. I hope this research yields data instead of conjecture.
Indiver716
The scientists better keep their Dannon away! Else, welcome to "The Stuff"! https://en.m.wikipedia.org/wiki/The_Stuff
ljaques
So the doctor told her it was an amazing-yet-dismal infection...
(I'm not sure we're ready for forced evolution.)
Pupp1
Before jumping onto the evolution conclusion, it is important to keep in mind that things like Darwin's Finches, are showing that there is a pre-set amount of variability. This seems to be in the epigenetic DNA, and is why Drawin's Finches can dramatically change their beak size and shape in a few generations. So, yeast may have this ability already pre-programmed into them.
anthony88
Can you imagine the size of the pizzas this will produce?! They'll cover a city block!