Our ancestor’s ‘leaky’ membrane answers big questions in biology
alphagalileo.org
alphagalileo.org
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.
> 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.
http://biocadmin.otago.ac.nz/pic/ATPaseanim.gif
Although it's more like a turbine than a crank. And if you're increasing the degree of a gradient of charged particles above what happens naturally, you're supercharging it!
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...
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?
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.
Could we in principle use some genetic engineering to make this process more efficient?
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.