
Our ancestor’s ‘leaky’ membrane answers big questions in biology - happyscrappy
http://www.alphagalileo.org/ViewItem.aspx?ItemId=144348&CultureCode=en
======
ascotan
Here's the actual article:
[http://www.plosbiology.org/article/info:doi/10.1371/journal....](http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001926)

tl;dr

The hypothesis here is that early bacteria/archea basically worked a lot like
a car battery, with a + and a - terminal and the the permeability of the cell
membrane allowed H+ to flow through the cell turning the little ATPase crank
to turn out ATP. The unspoken hypothesis here is that organisms like this
probably lived on the rock surface of a geothermal vent when there aqueous
phase was acidic and there was another 'layer' that was alkaline (probably on
the rock face?).

Overtime a Na+/H+ exchanger was added to increase the movement of H+ across
the membrane which made the ATPase crank turn 60% faster. Eventually in phase
3 ion pumps really supercharged the ion gradient and allowed these organisms
to move into environments that didn't need a bi-phasic H+/OH- layer. It's
likely that the ion pumps and non-permeable membranes formed as the little
guys moved out of the geothermal vents and diverged into new environments,
giving rise to the divergent archea and bacteria.

~~~
doctoboggan
The article specifies where they think the organism lived.

> Data from the study strongly suggest that LUCA lived in the area where
> ancient seawater, dense with positively charged particles called protons,
> mixed with warm alkaline vent fluid, which contained few protons. The
> difference in the concentration of protons across these two environments
> enabled protons to flow into the cell, driving the production of a molecule
> called adenosine triphosphate (ATP) which powered the growth of cells, just
> as it does today.

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fasteo
There are highly conserved molecular structures that made it to our DNA. This
is a good hint about the common origin of life.

Due to my genetic defect in the mitochondrial respiratory chain (ETC), this
one[1] caught my attention. Apart from its potential therapeutic application,
it shows how a xenotransplantation[2] at the molecular level can rescue a
defective molecular structure in a living creature that is orders of magnitude
more complex than the donor.

If you visualize the ETC as an engine with 5 different steps, with step 1
being broken, you go and get a repair piece from a much simple organism, a
yeast in this case, plug it in the receptor and, lo and behold, the engine
start working again.

And not only that, the piece from the donor serves the same function (pump
protons to complex II of the ETC), but it is "internally" much more simple.
This is a molecular "Lego" across species !!

[1]
[http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjourna...](http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0016288)

[2]
[http://en.wikipedia.org/wiki/Xenotransplantation](http://en.wikipedia.org/wiki/Xenotransplantation)

------
mrfusion
Would this tend to rule out panspermia since it looks like early life was
primitive and very specialized to conditions on certain locations of earth?

~~~
ufmace
It sounds like this work is fleshing out how one of the early steps in the
evolution of live took place. I'm guessing that the more we learn about the
links in this chain, the more we'll know about whether or not it's plausible
that there was some sort of panspermia.

------
idlewords
"My name is LUCA—I live on the deep sea floor"

~~~
twic
"I lived ancestrally to you. Yes, i think you've been me before."

------
jdnier
The actual article
([http://www.plosbiology.org/article/info:doi/10.1371/journal....](http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001926))
has a web simulation here:
[http://www.ucl.ac.uk/~rmhknjl/research/membranedivergence](http://www.ucl.ac.uk/~rmhknjl/research/membranedivergence)
([https://github.com/UCL/membranedivergence](https://github.com/UCL/membranedivergence))

------
scarmig
Naive question: are we anywhere near being close to reproduce this in the
laboratory?

As in, someone constructing something like the proposed primitive leaky LUCA,
showing that it could survive and reproduce in the described environment, and
then observing or engineering the changes that'd let it leave the vent?

Or is that far too ambitious to be realistic?

~~~
gus_massa
Building the environment is not so difficult, just a boiler, a water pump and
some mud. The production of the acid-basic gradient is more difficult. You
need some chemical compounds, they are neither rare nor expensive, but you
will probably need a lot of them to run a long time experiment. (Perhaps it's
easier than what I'm imagining now.)

It's very difficult to build a LUCA, in particular no one knows exactly how it
looked, no one knows the DNA, no one ... There are examples of genetically
modified bacteria, but they have only small changes, this is more difficult.
You must cut all that looks modern and hope that the remaining cell is capable
of surviving. Maybe add some other genes that look useful. I think that this
is almost impossible with the current technology and knowledge.

Another possibility is to just build the environment and throw some mud and
hope that something survives (perhaps it'd be easier with mud from a similar
natural place). The problem is that probably modern bacteria or modern archea
have evolved to live there and have eradicated the first LUCA versions
completely. So it's difficult to find the original living thing, but perhaps
the modern replacements can give some insight about the old thing.

------
hammock
How did the "bizarre, complex mechanism to harvest energy" evolve? Is there
any evidence of simpler ones that failed?

------
im3w1l
It is claimed that "all cells use the same bizarre, complex mechanism to
harvest energy".

Could we in principle use some genetic engineering to make this process more
efficient?

~~~
dredmorbius
Possibly. However evolution's been on that for a good long time -- about 3
billion years.

Where humans have succeeded in enhancing certain areas of biological
productivity, it's generally come at a cost in other areas, particularly
general robustness.

Another possibility would be to come up with an energy cycle _other_ than ATP,
though that would be equivalent to coming up with an independent biological
foundation, something you might want to think over at length.

~~~
whocares
The last time something akin to a new energy cycle happened on earth was when
cyanobacteria produced so much free oxygen it accumulated in the atmosphere
[0]. This caused a global extinction event and one of the longest ice ages
that the planet has known. So yes, we would need to be very careful playing
with non-ATP energy cycles...

[0] -
[https://en.wikipedia.org/wiki/Great_Oxygenation_Event](https://en.wikipedia.org/wiki/Great_Oxygenation_Event)

~~~
dredmorbius
One of my favorite examples of "whelp, looks like we done fooked over
t'environment"

