Hydrothermal vents, the first source of cell membrane material
John Telling, University of Newcastle
The origin of life on Earth and beyond is a mystery and perhaps one of the most important questions to answer. We know that life began simply. It probably began with a self-replicating chemical reaction based on something similar to the DNA molecule we rely on today to carry our genetic code. However, these reactions soon found a way to encase themselves inside an oil slick that could protect them from their surroundings and make the process more reliable and efficient. Hello, Cell was born. But where did membranes made of fatty acids come from in the first place? This question has puzzled biologists for decades. But now researchers at Newcastle University have recreated the conditions around hydrothermal vents, also known as underwater black smokers, in the lab. John Telling discovered that these conditions could spontaneously produce the very molecules scientists were looking for.
Jon – There is some evidence that these hydrothermal vents and hot springs are likely places where life originated. People have been trying to find out what the earliest cells, the origin of everything, looked like. And what we inferred from looking at genes is that the first cells, known as the “last universal common ancestor,” probably loved it. It lived on hydrogen gas, but would also have used carbon dioxide to build itself. So all of these lines of evidence point to these hot springs as possible origins of life.
Chris – It seems like we actually know quite a bit about what our ancestors are expected to be like. But what were the open questions you were trying to answer about that?
Jon – Previous people have tried to run various experiments to mimic some of the conditions that these hydrothermal vents would have been in. People have tried to recreate, for example, high temperatures, high pressures, or continuous flow like mixing seawater with this hotter fluid, but no one has actually tried to combine all of that at once. There was no one there. That's what we wanted to do. To achieve this, we created a new device in our laboratory. See if you can react this hydrogen gas and carbon dioxide on these metals to produce organic molecules by achieving high pressure, high temperature, and continuous flow, all in one experiment.
Chris – What kind of molecular source were you looking for?
Jon – We were particularly interested in molecules known as fatty acids. They have a fatty end and a water loving end. What's interesting is that if there are enough of them in water, they can form so-called membrane structures, known as vesicles or liposomes, but basically they are small round balls surrounded by form things. A membrane that separates what's inside and what's outside. Therefore, it is acting as a kind of first cell membrane, potentially separating the external environment from the internal environment and causing different chemical reactions.
Chris – I understand what you're trying to do with it because obviously that was a big issue. If life began as a series of chemical reactions, where did cells come from? So if there was a reaction that produced the oily sac that surrounds all of our cells, that's 90% of the equation .
Jon – Yeah, that's definitely a good step forward. It is the first step to creating a different self from the outside. I think the ability to do that and concentrate chemicals differently to the outside world and produce different reactions was an essential step for life to begin.
Chris – What is the feedstock that you are pretending to be a hydrothermal vent and what are the chemicals that end up coming out under these conditions?
Jon – What we supplied, the basis of it was hydrogen gas added under pressure. They then combined it with dissolved carbon dioxide. We react them on a mineral, in this case an iron-rich mineral known as magnetite, to form hydrocarbons, or organic molecules. In particular, they were looking for fatty acid molecules, which are a type of hydrocarbon.
Chris – How quickly can you get so much done?
Jon – The experiments we've run so far have only run for 16 hours, but in that time, yeah, we've generated enough to find them. If you run it longer, you may find that more organic molecules are produced, but you can be sure that there will be enough organic molecules to analyze.
Chris – Will they start coming together on their own? Because what you're saying is that fat parts love other fat parts, so they tend to come together. So are you starting to see that happening?
Jon – So far, no, because when they form, they actually form on the surface of the mineral. The next step in the experiment that we want to do is actually change the chemical conditions. We think that by making the environment more alkaline, we might be able to levitate some of these molecules, especially fatty acids, and hopefully watch them self-assemble.
Chris – If you were to bring your discovery to a party where people were already imagining how life began, your discovery of how these fatty acids begin to form and how people How do you connect and integrate what you were thinking about? Was it around the same time, about 4 billion years ago, that life began?
Jon – For example, people have previously discovered that these reactions proceed at higher temperatures. What we've done is run these experiments under conditions that are more realistic about what conditions were like on the early Earth. And I think it's more likely that these really important organic molecules were formed within these underwater hydrothermal vents. I also think it may deepen our understanding of how life originated elsewhere in the solar system and whether similar chemistry is occurring.
Chris – Of course, there's a mission to observe Europa, one of Jupiter's moons, so I thought I'd ask about that. People have also thought about Enceladus, one of Saturn's moons that appears to have a warm liquid ocean beneath its icy surface. Does that mean the conditions there could be similar to the conditions you're mimicking in the lab?
John – That's right. I think the most distinctive ocean so far is actually Saturn's moon Enceladus. A spacecraft known as Cassini was actually orbiting and actually sampled the plume that people think is being ejected into this ocean from beneath Enceladus' ice layer. A part of this ocean was actually blown into space and analyzed, and when they analyzed the vapor and particles contained in this plume, they found hydrogen gas and carbonate, so carbon dioxide was found there. It turns out there are signs that it exists. In the same way. We also analyzed a variety of organic molecules. It seems like potentially all the ingredients for the origin of life could be there, but considerable further experimentation is needed to narrow it down further.
