Energy Revolution was Key to Complex Life

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Energy Revolution was Key to Complex Life

 

ScienceDaily (Oct. 21, 2010) — The evolution of complex life is strictly dependent on mitochondria, the tiny power stations found in all complex cells, according to a new study by Dr Nick Lane, from UCL (University College London), and Dr William Martin, from the University of Dusseldorf.


"The underlying principles are universal. Energy is vital, even in the realm of evolutionary inventions," said Dr Lane, UCL Department of Genetics, Evolution and Environment. "Even aliens will need mitochondria."

For 70 years scientists have reasoned that evolution of nucleus was the key to complex life. Now, in work published in Nature, Lane and Martin reveal that in fact mitochondria were fundamental to the development of complex innovations like the nucleus because of their function as power stations in the cell.

"This overturns the traditional view that the jump to complex 'eukaryotic' cells simply required the right kinds of mutations. It actually required a kind of industrial revolution in terms of energy production," explained Dr Lane.

At the level of our cells, humans have far more in common with mushrooms, magnolias and marigolds than we do with bacteria. The reason is that complex cells like those of plants, animals and fungi have specialized compartments including an information centre, the nucleus, and power stations -- mitochondria. These compartmentalised cells are called 'eukaryotic', and they all share a common ancestor that arose just once in four billion years of evolution.

Scientists now know that this common ancestor, 'the first eukaryote', was a lot more sophisticated than any known bacterium. It had thousands more genes and proteins than any bacterium, despite sharing other features, like the genetic code. But what enabled eukaryotes to accumulate all these extra genes and proteins? And why don't bacteria bother?

By focusing on the energy available per gene, Lane and Martin showed that an average eukaryotic cell can support an astonishing 200,000 times more genes than bacteria.

"This gives eukaryotes the genetic raw material that enables them to accumulate new genes, big gene families and regulatory systems on a scale that is totally unaffordable to bacteria," said Dr Lane. "It's the basis of complexity, even if it's not always used."

"Bacteria are at the bottom of a deep chasm in the energy landscape, and they never found a way out," explained Dr Martin. "Mitochondria give eukaryotes four or five orders of magnitude more energy per gene, and that enabled them to tunnel straight through the walls of the chasm."

The authors went on to address a second question: why can't bacteria just compartmentalise themselves to gain all the advantages of having mitochondria? They often made a start but never got very far.

The answer lies in the tiny mitochondrial genome. These genes are needed for cell respiration, and without them eukaryotic cells die. If cells get bigger and more energetic, they need more copies of these mitochondrial genes to stay alive.

Bacteria face exactly the same problem. They can deal with it by making thousands of copies of their entire genome -- as many as 600,000 copies in the case of giant bacterial cells like Epulopiscium, an extreme case that lives only in the unusual guts of surgeonfish. But all this DNA has a big energetic cost that cripples even giant bacteria -- stopping them from turning into more complex eukaryotes. "The only way out," said Dr Lane, "is if one cell somehow gets inside another one -- an endosymbiosis."

Cells compete among themselves. When living inside other cells they tend to cut corners, relying on their host cell wherever possible. Over evolutionary time, they lose unnecessary genes and become streamlined, ultimately leaving them with a tiny fraction of the genes they started out with: only the ones they really need.

The key to complexity is that these few remaining genes weigh almost nothing. Calculate the energy needed to support a normal bacterial genome in thousands of copies and the cost is prohibitive. Do it for the tiny mitochondrial genome and the cost is easily affordable, as shown in the Nature paper. The difference is the amount of DNA that could be supported in the nucleus, not as repetitive copies of the same old genes, but as the raw material for new evolution.

"If evolution works like a tinkerer, evolution with mitochondria works like a corps of engineers," said Dr Martin.

The trouble is that, while cells within cells are common in eukaryotes, which often engulf other cells, they're vanishingly rare in more rigid bacteria. And that, Lane and Martin conclude, may well explain why complex life -- eukaryotes -- only evolved once in all of Earth's history.

 

http://www.sciencedaily.com/releases/2010/10/101020131700.htm

 

 

 

"Experiments are the only means of knowledge at our disposal. The rest is poetry, imagination." Max Planck


El-ahrairah
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Those capitalist eukaryotes!

Those capitalist eukaryotes! Those bourgeoisie will rue the day they perfected the use of mitochondria, exploiting poor cells that just happened to be absorbed into their wicked membranes! The proletariat prokaryotes will topple them from their undeserved evolutionary development! The revolution is upon us! TOVARISCH! DO SVIDAN YA!

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Atheistextremist
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Chuckle

 

Yes - we have enslaved the mitochondria. You want to hope they've forgotten about it these past 2.7 billion years and are not sitting around humming "By the Rivers of Golgi Body".

 

"Experiments are the only means of knowledge at our disposal. The rest is poetry, imagination." Max Planck


cj
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This is way over the top

This is way over the top cool and makes a lot of sense.


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cj wrote:This is way over

cj wrote:

This is way over the top cool and makes a lot of sense.

I don't even know what the hell it means!

Everything makes more sense now that I've stopped believing.


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Yeah guys

mellestad wrote:

cj wrote:

This is way over the top cool and makes a lot of sense.

I don't even know what the hell it means!

 

I'm reading a gigantic red book called The Cell at the moment - you know - it was the one on Amazon with the most stars. And as Melles says, what the fuck are they going on about? As the discussion drills down through the molecular structures of the cell to the chemistry beneath - the little understood input of sugars and all the rest of it - my head starts spinning like a top. The nice thing about this bit of research is that as cj says, it makes perfect sense. Without energy there's nothing happening and that means the absorption of energy producing bacteria must have come early in the program for the Eukaryotes.

You have to love cells. They are such complex beasties - their molecular complexity is far greater in many ways than the structural complexity of multicellular life. Being a sentient direct descendant of the first cells on earth beats the crap out of being formed from dust by a cosmic john bunyan with a bright blue arse.

 

 

 

 

 

"Experiments are the only means of knowledge at our disposal. The rest is poetry, imagination." Max Planck


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Atheistextremist wrote:By

Atheistextremist wrote:

By focusing on the energy available per gene, Lane and Martin showed that an average eukaryotic cell can support an astonishing 200,000 times more genes than bacteria.

"This gives eukaryotes the genetic raw material that enables them to accumulate new genes, big gene families and regulatory systems on a scale that is totally unaffordable to bacteria," said Dr Lane. "It's the basis of complexity, even if it's not always used."

"Bacteria are at the bottom of a deep chasm in the energy landscape, and they never found a way out," explained Dr Martin. "Mitochondria give eukaryotes four or five orders of magnitude more energy per gene, and that enabled them to tunnel straight through the walls of the chasm."

This is brilliant. Excellent article and discovery. Thinking about it in terms of energy availability per gene is something I'd never thought of before, but it makes a whole lot of sense.

By compartmentalizing energy production, and using the principle of modularity -- where the mitochondria can give up some functions that would be necessary if they lived independently, because the containing cell provides those functions for free -- the cost of having a high-energy cell goes way down. It's like having a fireplace inside your home, rather than sitting around a campfire in the open air. You need less wood to stay warm with a fireplace because it's kept in an enclosure. This makes cooking food easier and takes less energy, leaving more energy available for other stuff like making pottery and smelting metals to build better technology.

Never before did I see the case for saying that endosymbiosis is a major factor in evolution beyond standard genetic mutation and natural selection. In this case, two whole genomes combine to create a larger 'meta' genome, and hence a new organism altogether. The process occurs not by assimilating genes into your current DNA, but by wholesale adoption of a new complement of DNA.

I had always previously thought of endosymbiosis as the host organism acquiring and 'taming' an invading bacterium, but I think this new perspective of looking at the whole complex of the host cell combined with mitochondria as one energy-optimizing unit makes more sense out of the situation than seeing it as just the host alone being a separate entity 'utilizing' the mitochondria.

Amazing stuff.

Quote:

Cells compete among themselves. When living inside other cells they tend to cut corners, relying on their host cell wherever possible. Over evolutionary time, they lose unnecessary genes and become streamlined, ultimately leaving them with a tiny fraction of the genes they started out with: only the ones they really need.

The key to complexity is that these few remaining genes weigh almost nothing. Calculate the energy needed to support a normal bacterial genome in thousands of copies and the cost is prohibitive. Do it for the tiny mitochondrial genome and the cost is easily affordable, as shown in the Nature paper. The difference is the amount of DNA that could be supported in the nucleus, not as repetitive copies of the same old genes, but as the raw material for new evolution.

This is the key point. Cool.

 

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Good points, Natural.

natural wrote:

Never before did I see the case for saying that endosymbiosis is a major factor in evolution beyond standard genetic mutation and natural selection. In this case, two whole genomes combine to create a larger 'meta' genome, and hence a new organism altogether. The process occurs not by assimilating genes into your current DNA, but by wholesale adoption of a new complement of DNA.

I had always previously thought of endosymbiosis as the host organism acquiring and 'taming' an invading bacterium, but I think this new perspective of looking at the whole complex of the host cell combined with mitochondria as one energy-optimizing unit makes more sense out of the situation than seeing it as just the host alone being a separate entity 'utilizing' the mitochondria.

Amazing stuff.

 

Thanks.

 

 

 

 

"Experiments are the only means of knowledge at our disposal. The rest is poetry, imagination." Max Planck


cj
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mellestad wrote:cj

mellestad wrote:

cj wrote:

This is way over the top cool and makes a lot of sense.

I don't even know what the hell it means!

 

What Natural said.

I don't articulate my gut reactions well - especially when I'm in the middle of the "of course!" feeling.  And while I am interested in biology, I truly am not an expert.  So I don't have the analogies at my finger tips.  Ask me a computer question, I have lots of analogies for those type of questions.  I think Natural's fireplace analogy is great.

I was taught years ago that cells have membranes, a nucleus, organelles, a bunch of what I thought of - when I was in the 6th grade - as extraneous snot like egg whites, and oh, yeah, mitochondria.  In the early 60s, they knew that mitochondria had something to do with energy production.  They didn't seem sure it was the only source of energy in the cell. 

I also am partial to energy analysis over mechanical.  So looking at a cell from the view point of energy generating and moving through the system just makes more sense to me.  It also makes more sense to have an energy generator dedicated to that task - think of the difference between generating energy for every task rather than generating energy once and sharing the energy between all tasks.

It's just a really cool new way of looking at it all.  I am certain there will be a lot of arguments in academia over this idea and probably a lot of interesting additional research.

 

-- I feel so much better since I stopped trying to believe.

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cj wrote:I don't articulate

cj wrote:

I don't articulate my gut reactions well - especially when I'm in the middle of the "of course!" feeling.

Then let me help you: http://www.youtube.com/watch?v=X8u7px_GzWQ

"The Aim of an Argument...should not be victory, but progress."
-Joseph Joubert (1754-1824)

"All the world will be your enemy, Prince with a Thousand Enemies, and whenever they catch you, they will kill you. But first they must catch you, digger, listener, runner, prince with the swift warning. Be cunning and full of tricks and your people shall never be destroyed."
-Richard Adams, Watership Down, 1972


cj
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El-ahrairah wrote:cj wrote:I

El-ahrairah wrote:

cj wrote:

I don't articulate my gut reactions well - especially when I'm in the middle of the "of course!" feeling.

Then let me help you: http://www.youtube.com/watch?v=X8u7px_GzWQ

 

Reminds me of my German teacher - ganz genau!

 

-- I feel so much better since I stopped trying to believe.

"We are entitled to our own opinions. We're not entitled to our own facts"- Al Franken

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I guess I need to take a bio

I guess I need to take a bio 101 course sometime, so I at least understand the terminology!

 

Everything makes more sense now that I've stopped believing.