How the first cells formed in deep sea vents
It's a question no one's tired of asking - where did we come from, and how did life begin? One theory is that deep sea vents, where mineral-rich warm water issues from the planet’s interior, played a key role; here, the conditions could have been just right to allow simpler molecules to link up and form the crucial oil-based membranes that enclose cells. But nice though that theory was, no one had managed to prove that it was possible. Until now, that is. Because, by recreating conditions similar to a subsea vent in his lab, UCL's Sean Jordan has made it work. He told Katie Haylor how, and why these vents are so critical to the process...
Sean - So, they're really unique in that they're formed with an alkaline fluid and four and a half billion years ago when we think first life would have emerged, you have an acidic ocean and alkaline fluid inside a vent and it's almost like a battery - so a positive charge on one side negative on the other. This provides the energy that would allow you to create the first organic molecules and then you can go through stages of more complex chemistry. We can concentrate molecules inside of the vents because of their internal structure and you can form these non-living cells that eventually become living cells.
Katie - We've thought about hydrothermal vents and origin of life for a little while now. So, what was the specific problem you were trying to solve with this study?
Sean - There are many theories for the origin of life and alkaline hydrothermal vents have a lot going for them. In previous research no one has been able to form these cells under alkaline, salty conditions. So that's a big hit for this theory because if all life is cellular, we were able to form them for the first time and we think it's a being kind of boost for this theory.
Katie - How on earth do you make what came before the cell. What is that?
Sean - Modern cells are formed with phospholipids. So these are quite large molecules, they have tails that are hydrophobic which means they don't like water and heads that are hydrophilic, which do like water. When you put them in solution the hydrophobic tails connect, the hydrophilic head groups point outwards and then they form this sphere - looks like a soap bubble. We can see them on a microscope they look like a fatty sphere!
Katie - Are these just really, really, simple cells. How would these compare to a normal animal or plant cell, that we might see today?
Sean - Yeah. So they're super simple. So we've composed these using 14 lipids, so fatty acids, alcohols, and isoprenoids. A modern cell would be composed of many different types of phospholipids, so again larger molecules but you would also have proteins in there as well. So, these are all different molecules that would make up a cell membrane and cell membranes in modern cells are completely active in working with metabolism - allowing things in and out. What these simple cells are like, they're actually quite leaky, so that's good because when you don't have an active way of passing things across the membrane. If the cell itself is leaky, things can get across without needing to do any work essentially. But if we can get simple enzymes like protein, into this membrane then it can start to play a role in metabolism.
Katie - Okay. That might take us a bit closer to the cells that we know and love today.
Sean - Exactly.
Katie - How did you manage then to make these cellular precursors in the conditions that you have, that people haven't been able to do before.
Sean - The reason that we think that people haven't been able to do it before, is because the approach that's been taken is a kind of standard chemistry approach where everything is kept really clean. They were using one, two, and three molecules to make cells putting them under really harsh environmental conditions of high temperatures, varying P.H and different salts. These simple cells they don't like it, but the good thing is that at the origin of life you would have had close to a hundred of these types of molecules. So, we thought let's make things a bit more messy a bit more realistic! So we just used 14 different lipids and we mixed them together and they were able to be stable under these conditions.
Katie - Ok, so you've got a bigger variety of starting components as it were. What about the actual conditions? Because these vents are hot, alkaliney and salty - right?
Sean - A lot of people confuse them with these black smoker vents, with violent black smoke coming out. They're around three hundred and fifty degrees, it's much more difficult to try and form any sort of life in those but what alkaline vents have, you're talking around 50 to 100 degrees - we used 70 degrees. Seawater concentrations of salts because that's the best approximation we can have for what they see the ocean would have been like back then and then the alkalinity of around P.H. 11 page 12, we've used that's representative again of the fluids in the inside.
Katie - Now without getting too philosophical, these precursors aren't actually alive, right?
Sean - they're absolutely not alive.
Katie - What does being able to do this process tell us about how life may have started in the first plac?
Sean - All we can do is think about what life requires, even that in itself is a controversial topic! So, most people don't agree on what's alive and what's not, but we can take simple things, like DNA, cell membranes, metabolism and we can try and replicate each of those by themselves in the lab - then we can start to think about putting these together. If you can get all of those components to work under conditions that are representative of your theory, then that lends more weight to the idea that could have been where life emerged.