Nick Lane: prediction

Transcript context

…I’ll tell you how I got there first. I started out working on mitochondria. That took me into the evolution of eukaryotes. Eukaryotes acquire these endosymbionts that become mitochondria and they change the potential of evolution. It doesn’t change everything immediately, but it changes where the endpoints can be. It allows the evolution of these large, complex cells and eventually multicellular organisms and us. What are mitochondria actually doing? What they’re actually doing is respiration. They’re generating energy for cells. They’re doing plenty of other things as well, but the main thing we can think about is they’re the energy producers. They’re derived from bacteria, and bacteria produce their energy in exactly the same way. They’re generating energy by generating an electrical charge on the membrane. That charge is small, but the membrane’s really thin. The charge is about 150 to 200 millivolts, but the membrane is five nanometers in thickness, so that’s five millionths of a millimeter. If you shrank yourself down to the size of a molecule and stood next to that membrane, you would experience 30 million volts per meter, which is equivalent to a bolt of lightning. That’s the strength of the force of the voltage across the membrane, which is colossal. It’s generated by really sophisticated proteins that pump protons across the membrane. Then it’s ATP synthase, which is pretty much universal, and it’s a rotating nanomotor that sits in the membrane. This is colossally complex, interesting machinery, and it’s universally conserved. It’s as conserved as, say, a ribosome, the protein-building factory. It’s pretty much everywhere across life. You wonder, how on earth did life come to be that way? If it’s conserved universally across life, it looks like it goes right back to the common ancestors of all cells. So there’s the question. How did it arise in the first place? That was, for me, tremendously thrilling because it’s a way in, as a researcher, to the origin of life. How did these energy-generating systems arise in the first place? My way in was, the gates were opened by Bill Martin and Mike Russell who, around the early 2000s, were publishing some amazing papers together. They were saying that in this deep-sea hydrothermal vent, rather than it being like a black smoker with a chimney with smoke belching out of the top, it’s like a mineralized sponge with lots of pores that are cell-like in their structure. You’ve got an acidic early ocean. You’ve got alkaline fluids coming out of these. You’ve got mixing going on in this whole system. You could at least imagine that you’ve got a pore in here which is a bit like a cell in terms of its size and its shape. On the outside, you’ve got acid ocean waters percolating in, and on the inside, you’ve got these hydrothermal fluids. So you’ve got a barrier, you’ve got an inside and an outside, and you’ve got more protons outside coming in, potentially driving work. ting in, and on the inside, you’ve got these hydrothermal fluids. So you’ve got a barrier, you’ve got an inside and an outside, and you’ve got more protons outside coming in, potentially driving work. It’s very much like a cell is structured. The other thing is, what are these minerals? You’ve got these mineralized pores with minerals. The minerals, we think, on early Earth would have been a lot of metals in there, things like iron sulfide or nickel sulfides and things like that. The reason that’s important is that what plant cells do, but also what autotrophic bacteria do, is they take CO2 and they take hydrogen and they react them together to make all the building blocks of life. Plants get the hydrogen from water, H2O. They take the H2 out of water and throw away the oxygen, and that collects in the atmosphere. But what bacteria very often do is that they have got hydrogen bubbling out of a hydrothermal vent. They just take the hydrogen straight as gas, and they react it with CO2 and they make all the building blocks of life. What are the enzymes that they use to do that? They’re very often using these same metals that you would have found in the early oceans—nickel and iron and so on. How are they powering the reaction between hydrogen and CO2? They’re using this membrane potential, the electrical potential—the difference in protons between the outside and the inside—to drive that work, effectively, to power the reaction between hydrogen and CO2 to make organics and drive growth. This was all in place before I came along. This was coming from Mike Russell and Bill Martin. The details are very uncertain. Whether or not you can really drive any biochemistry that way is very uncertain. But it’s a thrilling idea because you’ve got a continuity between a geological environment and cells as we know them. If it did emerge that way, then it would say, “Here’s why bacteria have got this charge on their membrane,” because it was there in a hydrothermal vent from the beginning. It always powered work from the very beginning. That’s why, in the end, an endosymbiosis that gives rise to eukaryotes would free you from the constraints of generating a charge on the membrane. Now you internalize that in eukaryotes, and now you’re free to become larger and more complex. You’ve gone from thinking about a puzzle about why eukaryotes are special to thinking about planetary systems and thinking about the origin of life. What are the forces that are going to give rise to life, how would that constrain life, and would we see the same things on other planets or something different? What are the fundamental reasons that it works this way? It becomes astrobiology, really. It’s a thrilling change of perspective to come from my own background, which was to do with mitochondrial biology, an organ transplantation once upon a time, and spinning on a pinhead, you end up working on the origin of life. It’s fantastic. It’s so fascinating. Just to recapitulate, for my own understanding and the audience’s, let’s just break down what we have here. You have the analog of a cell in these pores. You have something which concentrates the buildup of these organics so that they don’t just all diffuse in some big primordial soup. This is why you think some primordial lake is not where this happened. It had to be concentrated in some entity. Then you’ve got a chemiosmotic gradient, a proton gradient, which drives work. Specifically, it favors the fixation of carbon dioxide to drive the reaction with hydrogen gas to make organics. Then you’ve got, along this membrane, catalysts, which are basically early enzymes. You’ve got enzymes, you’ve got the cell, you’ve got the proton gradient. The story is that you make very simple organics with CO2 and H2, and then those simple organics are then recatalyzed to make more and more complex organics, and TL;DR, metabolism, fatty acids, and nucleotides, everything else.…

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