Lab yeast make evolutionary leap to multicellularity

[Geriatrix]

http://www.newscientist.com/article...ke-evolutionary-leap-to-multicellularity.html

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.

Multicellularity has evolved at least 20 times since life began, but the last time was about 200 million years ago, leaving few clues to the precise sequence of events. To understand the process better, William Ratcliff and colleagues at the University of Minnesota in St Paul set out to evolve multicellularity in a common unicellular lab organism, brewer's yeast.

Their approach was simple: they grew the yeast in a liquid and once each day gently centrifuged each culture, inoculating the next batch with the yeast that settled out on the bottom of each tube. Just as large sand particles settle faster than tiny silt, groups of cells settle faster than single ones, so the team effectively selected for yeast that clumped together.

Sure enough, within 60 days - about 350 generations - every one of their 10 culture lines had evolved a clumped, "snowflake" form. Crucially, the snowflakes formed not from unrelated cells banding together but from cells that remained connected to one another after division, so that all the cells in a snowflake were genetically identical relatives. This relatedness provides the conditions necessary for individual cells to cooperate for the good of the whole snowflake.

"The key step in the evolution of multicellularity is a shift in the level of selection from unicells to groups. Once that occurs, you can consider the clumps to be primitive multicellular organisms," says Ratcliff.

In some ways, the snowflakes do behave as if they are multicellular. They grow bigger by cell division and when the snowflakes reach a certain size a portion breaks off to form a daughter cell. This "life cycle" is much like the juvenile and adult stages of many multicellular organisms.

After a few hundred further generations of selection, the snowflakes also began to show a rudimentary division of labour. As the snowflakes reach their "adult" size, some cells undergo programmed cell death, providing weak points where daughters can break off. This lets the snowflakes make more offspring while leaving the parent large enough to sink quickly to the base of the tube, ensuring its survival. Snowflake lineages exposed to different evolutionary pressures evolved different levels of cell death. Since it is rarely to the advantage of an individual cell to die, this is a clear case of cooperation for the good of the larger organism. This is a key sign that the snowflakes are evolving as a unit, Ratcliff reported last week at a meeting of the Society for the Study of Evolution in Norman, Oklahoma.

Other researchers familiar with the work were generally enthusiastic. "It really seemed to me to have the elements of the unfolding in real time of a major transition," says Ben Kerr, an evolutionary biologist at the University of Washington in Seattle. "The fact that it happened so quickly was really exciting."

Sceptics, however, point out that many yeast strains naturally form colonies, and that their ancestors were multicellular tens or hundreds of millions of years ago. As a result, they may have retained some evolved mechanisms for cell adhesion and programmed cell death, effectively stacking the deck in favour of Ratcliff's experiment.

"I bet that yeast, having once been multicellular, never lost it completely," says Neil Blackstone, an evolutionary biologist at Northern Illinois University in DeKalb. "I don't think if you took something that had never been multicellular you would get it so quickly."

Even so, much of evolution proceeds by co-opting existing traits for new uses - and that's exactly what Ratcliff's yeast do. "I wouldn't expect these things to all pop up de novo, but for the cell to have many of the elements already present for other reasons," says Kerr.

Ratcliff and his colleagues are planning to address that objection head-on, by doing similar experiments with Chlamydomonas, a single-celled alga that has no multicellular ancestors. They are also continuing their yeast experiments to see whether further division of labour will evolve within the snowflakes. Both approaches offer an unprecedented opportunity to bring experimental rigour to the study of one of the most important leaps in our distant evolutionary past.

 

[Praeses]

Yeasts are just a unicellular phases of normal moulds, so i don't get what the fuss is about. Moulds are multicellular. If you buy blocks of bakers yeast they should be in hyphal form if I'm not mistaken.

 

[boramk]

Yeasts are just a unicellular phases of normal moulds, so i don't get what the fuss is about. Moulds are multicellular. If you buy blocks of bakers yeast they should be in hyphal form if I'm not mistaken.

I don't think you got it. It went from a single cell organism to a multicellular organism, there is a HUGE difference and has nothing to do with your baking utensils.

Single cellular organism = Malaria, an amoeba; a very small cell, usually but not limited to prokaryotes
Multicellular = eukaryotes, animals, plants

This is a huge jump in evolution, to say because its only a small creature it doesn't mater is foolish. This is equivalent to humans growing wings and a gill

 

[Praeses]

I don't think you got it. It went from a single cell organism to a multicellular organism, there is a HUGE difference and has nothing to do with your baking utensils.

Single cellular organism = Malaria, an amoeba; a very small cell, usually but not limited to prokaryotes
Multicellular = eukaryotes, animals, plants

This is a huge jump in evolution, to say because its only a small creature it doesn't mater is foolish. This is equivalent to humans growing wings and a gill

Wtf are you on about?
Fungi are eukaryotic. Fungi consist of moulds and yeasts. Yeasts are unicellular phases of hyphal fungi i.e. Moulds.
When you buy bakers yeast in block-form, i.e. Saccharomyces sp., you buy the Yeast in its hyphal form.

 

[boramk]

Wtf are you on about?
Fungi are eukaryotic. Fungi consist of moulds and yeasts. Yeasts are unicellular phases of hyphal fungi i.e. Moulds.
When you buy bakers yeast in block-form, i.e. Saccharomyces sp., you buy the Yeast in its hyphal form.

Can you read??

The article says "single celled yeast". Yeast is a single celled organism, it is NOT multicellular.
Why are you going on about the hypahl form now? Read my OP, it seems you are confused.

 

[HapticSimian]

Ahem...

Yeasts are unicellular, although some species with yeast forms may become multicellular through the formation of a string of connected budding cells known as pseudohyphae, or false hyphae, as seen in most molds.

source

I think it's safe to say we're talking about a strictly unicellular variety here, otherwise it wouldn't be worth reporting on.

 

[Praeses]

Ahem...



I think it's safe to say we're talking about a strictly unicellular variety here, otherwise it wouldn't be worth reporting on.

The thing is, they used brewer's yeast which to my knowledge has a hyphal form.

 

[HapticSimian]

The thing is, they used brewer's yeast which to my knowledge has a hyphal form.

It depends. Several species are classified as such.

I'm gonna go out on a limb here and suggest the relevant evolutionary biologists conducting the research would probably be a little more certain of their facts than you give them credit for. Either that, or they're mildly retarded.

I'll wait for PZ Myers to weigh in on it.

 

[porchrat]

Wow very cool. Interesting to see that it isn't just a colony but division of labour is occurring too.

 

[luxe]

I bet that yeast would make great beer...

 

[Geriatrix]

I bet that yeast would make great beer...

From you...

 

[Naks]

And yet religious nutcases will still harp on about how evolution is 'just a theory' #SMH

 

[porchrat]

And yet religious nutcases will still harp on about how evolution is 'just a theory' #SMH

I suppose if it doesn't grow legs or turn into a helicopter or something it isn't "macroevolution" or whatever misunderstood garbage those that don't comprehend evolution go on about.

 

[Geriatrix]

I suppose if it doesn't grow legs or turn into a helicopter or something it isn't "macroevolution" or whatever misunderstood garbage those that don't comprehend evolution go on about.

I see the ID crowds already shouting "pre-adaption" on this particular species. Seems like a followup experiment is on its way.

 

[Ancalagon]

I suppose if it doesn't grow legs or turn into a helicopter or something it isn't "macroevolution" or whatever misunderstood garbage those that don't comprehend evolution go on about.

And it needs to "evolve" legs and eyes without having any children, since they never get that the transitions are gradual.

 

[porn$tar]

But this still doesn't explain the immaculate conception and virgin birth!!111!!11!!!

 

[Praeses]

I'm not aiming this at anybody in particular, but some of the people on this forum try to see evolution everywhere, just like religious folk see their deities everywhere. The problem is that science is open for debate, and I bet it's not only ID people shouting preadaptation but lots of scientists too. Possible flaws in hypotheses need to be challenged, science is there to find the answers. Quit jumping to conclusions without thinking critically. I'm not shooting down this article, since the probability of new "scientist" reporting on scientific articles badly is quite high

 

[porchrat]

I'm not aiming this at anybody in particular, but some of the people on this forum try to see evolution everywhere, just like religious folk see their deities everywhere. The problem is that science is open for debate, and I bet it's not only ID people shouting preadaptation but lots of scientists too. Possible flaws in hypotheses need to be challenged, science is there to find the answers. Quit jumping to conclusions without thinking critically. I'm not shooting down this article, since the probability of new "scientist" reporting on scientific articles badly is quite high

Dude even if the yeast retained elements of multicellularity and therefore had a smaller barrier to overcome to develop multicellularity it still demonstrates that the jump to multicellularity from unicellularity could be much easier than we ever thought. The claims of preadaptation are for sure something to consider but they don't change that evolution has occurred here and those changes have resulted in a shift from unicellular behaviour to multicellular behaviour. So after looking at that previous sentence to claim that people are "try[ing] to see evolution everywhere" as though it isn't actually there is just stupidity. Sorry mate.

 

[Praeses]

Dude even if the yeast retained elements of multicellularity and therefore had a smaller barrier to overcome to develop multicellularity it still demonstrates that the jump to multicellularity from unicellularity could be much easier than we ever thought. The claims of preadaptation are for sure something to consider but they don't change that evolution has occurred here and those changes have resulted in a shift from unicellular behaviour to multicellular behaviour. So after looking at that previous sentence to claim that people are "try[ing] to see evolution everywhere" as though it isn't actually there is just stupidity. Sorry mate.

Many yeasts have multicellular phases - including baker's/brewer's yeast (Saccharomyces cerevisiae) which was used in the study!! What I meant by the evolution comment isn't that evolution isn't everywhere, it's just that people make such a fuss about the smallest things which are quite common if you actually do any form of biological research.

Some time ago people also made such a fuss about some E. coli gaining the ability to grow on citrate. I have an E. coli isolate which can grow on citrate. It's not a big adaptation since citrate (aka citric acid) is part of aerobic respiration's citric acid cycle.

It just bores me how people get all uber excited about stupid things

 

[porchrat]

Some time ago people also made such a fuss about some E. coli gaining the ability to grow on citrate. I have an E. coli isolate which can grow on citrate. It's not a big adaptation since citrate (aka citric acid) is part of aerobic respiration's citric acid cycle.

So you've ignored this part of my post: "Dude even if the yeast retained elements of multicellularity and therefore had a smaller barrier to overcome to develop multicellularity it still demonstrates that the jump to multicellularity from unicellularity could be much easier than we ever thought. The claims of preadaptation are for sure something to consider but they don't change that evolution has occurred here and those changes have resulted in a shift from unicellular behaviour to multicellular behaviour."

You basically just reworded it using E. coli and citrate. The ability to grow on citrate WAS developed. Sure there may have been portions of it still hanging around but it STILL evolved. To then claim that people are trying to "see evolution everywhere" as though there isn't evolution occurring there makes me go :wtf:.