Evolution of Multicellularity In Lab Yeast

November 9, 2012 11:55 AM

In just a few weeks single-celled yeast have evolved into a multicellular organism, complete with division of labour between cells. This suggests that the evolutionary leap to multicellularity may be a surprisingly small hurdle. More from Scientific American blogs. [Full Text PDF of the Publication of Note]

More from the lab, with videos:

Snowflake reproduction 2:The snowflakes reproduce by spitting out "propagules" once they reach a large size. Once the propagule has grown (through a series of cell divisions) to be large enough, it too spits out a new propagule.

Snowflake settling: The multicellular yeast clusters look like "snowflakes" as they settle to the bottom of their container.

Snowflake genetic stability: Single cells of snowflake-phenotype yeast regenerate new snowflake-phenotype clusters.

Snowflake size evolution: Time-lapse microscopy of derived rapid settling (left) and slow settling (right) genotypes isolated from 5 minute and 25 minute settling regimes, respectively. Cultures were grown for 24 h, diluted 300-fold, and grown in 0.5 uL YPD. Time-lapse microscopy was performed with images taken every minute for 600 minutes.

The actual paper is very accessibly written and totally understandable by the average non-creationist:

Experimental evolution of multicellularity (PDF)
Multicellularity was one of the most significant innovations in the history of life, but its initial evolution remains poorly understood. Using experimental evolution, we show that key steps in this transition could have occurred quickly. We subjected the unicellular yeast Saccharomyces cerevisiae to an environment in which we expected multicellularity to be adaptive. We observed the rapid evolution of clustering genotypes that display a novel multicellular life history characterized by reproduction via multicellular propagules, a juvenile phase, and determinate growth. The multicellular clusters are uniclonal, minimizing within-cluster genetic conflicts of interest. Simple among-cell division of labor rapidly evolved. Early multicellular strains were composed of physiologically similar cells, but these subsequently evolved higher rates of programmed cell death (apoptosis), an adaptation that increases propagule production. These results show that key aspects of multicellular complexity, a subject of central importance to biology, can readily evolve from unicellular eukaryotes..

posted by Blasdelb (18 comments total)

The videos are very short, very pretty, and very awesome once you get how really crazy what the yeast are doing is.

Also, not everyone is super stoked, the response and comments are particularly interesting.
posted by Blasdelb at 12:02 PM on November 9, 2012 [1 favorite]

wha, awesome!
posted by leotrotsky at 12:04 PM on November 9, 2012

I'm trying to decide whether it was funny or tacky to have the whole story get blocked for a moment by a pop-up promoting Monistat.
posted by EmpressCallipygos at 12:06 PM on November 9, 2012 [8 favorites]

I for one welcome our new yeast overlords.
But I seriously hope this won't lead to beer suddenly developing consciousness and refusing to be consumed by me.
posted by Hairy Lobster at 12:12 PM on November 9, 2012 [3 favorites]

Does this yeast make more alcohol? Is it better for beer, yeast, champagne, distillables, commercial fermentation? IMPORTANT THINGS.
posted by mkb at 12:12 PM on November 9, 2012 [2 favorites]

Yeah, but you just try and get a single-celled yeast to do the dishes once and a while!
posted by The 10th Regiment of Foot at 12:21 PM on November 9, 2012

That's the craziest thing I've heard all day, thanks Blasdelb.
posted by Scientist at 12:31 PM on November 9, 2012

This suggests that the evolutionary leap to multicellularity may be a surprisingly small hurdle.

It suggests that formerly multicellular organisms don't completely lose that ability.

There's no good reason to believe that multicellularity evolved from scratch here.
posted by nixt at 12:35 PM on November 9, 2012 [2 favorites]

Forget the snowflake yeast, I'm more impressed by the calm, fact-based discussion of the paper's merits in the comments on the Discover blog. Kudos to the participants.
posted by superelastic at 12:47 PM on November 9, 2012

Special snowflakes indeed. A few divisions more and they'll be all over AskMefi asking "cell relations" questions.
posted by elgilito at 12:56 PM on November 9, 2012 [2 favorites]

Forgive me if I'm understanding the paper wrong, but it is interesting that the experiment is so simple. It sounds like you could do that in high school. Whether the outcome is right or wrong I don't know, but I guess that they will do it again with lots of different yeasts to see what happens.


Also, this paper: Boraas ME, Seale DB, Boxhorn JE (1998) Phagotrophy by a flagellate selects for colonial prey: A possible origin of multicellularity. Evol Ecol 12(2):153–164, sounds awesome. Just the thought that multicelledness evolved to stop us from being eaten.
posted by Jehan at 1:01 PM on November 9, 2012 [1 favorite]

I for one welcome our new yeast leavened overlords.
posted by JaredSeth at 1:06 PM on November 9, 2012

Resisting the urge to link to any one of several related horror films is making me twitch. But, I'll leave this here instead.
posted by CynicalKnight at 1:13 PM on November 9, 2012

"It suggests that formerly multicellular organisms don't completely lose that ability.

There's no good reason to believe that multicellularity evolved from scratch here."

This is from the Primary Investigator of the work:

"Our yeast are not utilizing ‘latent’ multicellular genes and reverting back to their wild state. The initial evolution of snowflake yeast is the result of mutations that break the normal mitotic reproductive process, preventing daughter cells from being released as they normally would when division is complete. Again, we know from knockout libraries that this phenotype can be a consequence of many different mutations. This is a loss of function, not a gain of function. You could probably evolve a similar phenotype in nearly any microbe (other than bacteria, binary fission is a fundamentally different process). We find that it is actually much harder to go back to unicellularity once snowflake yeast have evolved, because there are many more ways to break something via mutation than fix it. The amazing thing we see is that we rapidly see adaptations to this adaptation. If we select for more rapid settling, snowflake yeast evolve to delay reproduction until the parent is larger, allowing it settle more quickly. We see the evolution of higher rates of apoptosis as a way to regulate the size and number of propagules produced. We show that the transition to multicellularity in yeast is surprisingly easy, and have no reason to suspect it would be any harder in other microbes with a reproductive process similar to yeast."

posted by Blasdelb at 2:31 PM on November 9, 2012 [1 favorite]

"Does this yeast make more alcohol? Is it better for beer, yeast, champagne, distillables, commercial fermentation? IMPORTANT THINGS."

Outside of the very particular conditions that were used to evolve these strains, the yeast are actually meaningfully harmed by their conversion to multicellularity, however a very interesting potential use did just occur to me. It is commonly said that amateur homebrew beers all taste the same, because they are all unfiltered and thus have a strong taste of yeast over any other beer flavors. With beers that are not meant to have yeast in them, the brew is left to mature for extended periods of time so that the yeast sediments as it reaches stationary phase and the beer is siphoned off - often more than once. If these mutations lead to significantly higher sedimentation rates, then beer could be made better for brewers who operate at a scale below what is needed for yeast filters to make sense.

As Jehan mentioned, this would be totally doable at home with a homemade centrifuge, the microscopes in my lab, and some good asceptic technique. I'll report back if I can get it to work and then see how well it makes beer.
posted by Blasdelb at 2:48 PM on November 9, 2012 [6 favorites]

But I seriously hope this won't lead to beer suddenly developing consciousness and refusing to be consumed by me.

Only until it realizes that it can do much more damage from within.

Beware the TROJAN BEER!
posted by delfin at 2:57 PM on November 9, 2012 [1 favorite]

Slightly related: (by mefi's own jscalzi): When the Yogurt took over
posted by Hactar at 3:12 PM on November 9, 2012 [1 favorite]

I got it to work with a decent lager strain of yeast, now all I need to do is see if the beer turns out well.
posted by Blasdelb at 6:54 AM on November 20, 2012