Titans of Science: Antje Boetius
Titans of Science continues with the microbiologist who discovered how an extraordinary relationship between two methane-eating seafloor species has shaped the world we know today. To explain that and much more is the ocean aficionado Antje Boetius…
In this episode

00:55 - Antje Boetius: The call of the deep sea
Antje Boetius: The call of the deep sea
Antje Boetius, AWI
Antje Boetius was born on the 5th of March 1967 in Frankfurt in what was then West Germany. She grew up there, attending Schillerschule and the Justus von Liebig Gymnasium, both of which are in Darmstadt, but enjoyed many opportunities to escape for a holiday at the seaside.
She studied Biology at the University of Hamburg as an undergraduate, and received her PhD from the University of Bremen in 1996. During that time, she undertook 14 deep sea expeditions across the world’s oceans, but that number is now closer to 50.
Antje then joined the Max Planck Institute for Marine Microbiology first as a post-doc, and then as an assistant professor. She is currently the Director of the Alfred Wegener Institute, which conducts climate and marine research in polar and high latitude waters.
Antje’s work has focused on deep sea microbiology, and she was the first person to describe anaerobic oxidation of methane, a process by which some species of microbe can subsist without atmospheric or dissolved oxygen by splitting apart sulphate molecules for the oxygen therein. The discovery of this process has highlighted the importance of keeping our seafloors pristine, as well as the role these microbes played in making earth habitable for us.
Antje - I wasn't exactly a kid that would go play in the mud a lot or play outside, or play soccer or something. I was reading books all the time and in the book reading, I loved books that were about adventure. I totally loved Jules Verne's 20,000 Leagues Under the Sea, and I think I read it a hundred times or so. And I developed this fantasy of myself becoming a world ocean explorer and maybe also inspired by my grandfather, who was a captain, and maybe also by other people in my family that talked about the sea. But then also being a kid at the seaside, in any vacation my parents could take, we would go camping. And I always had this feeling I belong in the ocean. And so all of this together made this fantasy or this utopia of myself becoming a deep sea researcher. And today I'm a very happy person because I can say what I dreamt as a kid has become reality.
Will - Interesting that you mentioned your grandfather, of course, a navigator on the Hindenburg, and it kind of perhaps shows that navigation and exploration ran in your family.
Antje - <laugh>. Yeah. If there would be a gene for that. My grandfather, he often told us kids about the hard times when he was a young man and it was unemployment and poverty in Germany. Then of course the ugly war coming up, he lived between the two wars as a sailor. They were taken for the submarines, they were taken for the zeppelins. And it was all a story of the preparation of war in Germany. And so it was not actually that he meant to explore because he was curious. It was a matter of surviving and he simply trusted the ocean. He trusted his profession as a seamen to go on Zeppelins, because navigation skills were needed there as similar to what it is at sea.
Will - Good then that your research has become more of a scientific one then.
Antje - Yes, it's true <laugh>, but it's still this idea that we have this planet Earth, which is mostly ocean, and it is so unstudied that you have one dive to the deep sea, and you see some type of life that no one ever has seen before or will ever see again. Or you have an expedition and you make findings simply because it's so understudied. So in a way it is of course very hard natural science, but it is also discovery. It is also an adventure because just knowing that the next finding is looming around the corner is fascinating for a profession.
Will - Yes, I mean, I've met many marine biologists as part of my past life as a marine biologist across all various disciplines of marine biology. I think very few of them would be too keen to take a trip in a deep sea submersible, let alone how many you've been on. What is it about such a human hostile environment that fascinates you?
Antje - Yeah, the dive itself. So if you work with a manned submersible, it is the special experience of travelling into the deep. But what fascinates me is really the perspective that is simply the way towards the goal of your research. For example, the sea floor, in my case, it's a long way and you have to prepare for it. And then as you sink into the deep, it gets dark outside, life is different. You see organisms, you see the bioluminescence around you, and by that you have these two hours to focus on your work and you understand what it means, this giant dark space that the ocean is. And I love that. I love that situation of starting the research by travelling towards the depth of the oceans, having time to look outside and living a little bit of this dream of Captain Nemo <laugh> in 20,000 Leagues Under the Sea <laugh>.
Will - You're painting it far more romantically. You're almost winning me over, I think. And I feel compelled to ask, given the amount of dives you've been on, what would you say is the coolest thing you've seen?
Antje - Oh, there's so many cool things. I mean, I always love the interaction with octopods, the kraken, because they're such curious beings. And to think of an organism that is actually just has a little bit different of a bauplan, a different form of life as a mussel is, or a clam or a snail, but because they have these neurons that that already form part of a brain in their head, and because they also have independent brains in the legs, they are a very curious, special human-responding life forms. And I love that when one dives almost always, where you meet one of these octopods and that interaction is to me, always the best. But then the landscapes also, I just love to dive into the deep sea and work at the salt lakes because you're in the water and you see water in the water because of the different densities. And so that is always very curious, the situation that you're already swimming in the water and then you see a lake. That's cool.
Will - Those are some great perks of the job <laugh>, but it probably wasn't what you had done there looking for.

07:24 - Antje Boetius: Discovering methane-munching microbes
Antje Boetius: Discovering methane-munching microbes
Antje Boetius, AWI
In this edition of The Naked Scientists, deep sea microbiologist Antje Boetius explains how she discovered methane-consuming microbes, and why the seafloor is such a precious and important ecosystem...
Will - What were you down there looking for at the bottom of the ocean?
Antje - In various missions, the purpose was to find sea floor areas with a lot of methane where we could extract, find the so-called methanotrophs. So organisms, microorganisms, that feed on methane without using oxygen. And to find them, we looked for special cues in the landscape, for example, that a lot of methane would bubble out because it means there is a lot of methane under high pressure that can dissolve in the water and that will then enrich the microbes that eat the methane. And so that's why we were looking for such spots. And that brings you to extreme environments that are quite funky because they bubble and they have bacterial mats or huge assemblies of animals that feed on bacteria. And that was mostly the type of research I did, finding those spots and finding the microbes I needed to work with on land in a laboratory.
Will - How did you even know what to look for though? Because if you said, to me, I think there's going to be microbes at the bottom of the sea that are unlike any others that don't need oxygen to subsist. How do you go about theorising that and then going down to find them?
Antje - If you're a microbiologist, then you know that nature has microbes of specific functions where exactly the energy sources are right. So if I look for a microbe that should eat methane without oxygen, where would you go? You would go to a place that has a lot of methane and no oxygen, for example, in deep basins that have no oxygen like in the plexi or in sediments that have lots of organic matter so that oxygen is consumed. So basically that is part of our expertise. If we know what microbes we are looking for, we know what landscapes to look for.
Will - So how do these work then, these microbes?
Antje - Yeah, so the surprising thing is for decades some geologists had an idea of what to look for when one would look for these methane-munching microbes, it was considered by the microbiologists that it couldn't be that microbes would eat methane without oxygen for the energy, the low energy that would be provided to the microorganisms to thrive, to grow, to fix CO2. And so the geologist had traces, the microbiologists said, 'impossible, biology can't do such things.' But I did exactly what I said. So I thought if I were to find such microorganisms, I must go to the place in the sea with the most abundant methane for very long times and the least availability of oxygen. And it was a time when there was a lot of excitement finding gas hydrates, so frozen methane in the sea floor. And so I was on one of those expeditions where the geologist wanted to map out the surface near gas hydrates. And I thought, that's where I need to look, because if there is so much methane that it is frozen as ice in the sea floor, there should be the microbes eating it because they would not find another place where there would be so much food for them.
Will - And I'd be naïve to assume that you did your experimental work on the sea floor, but once you'd taken your samples back up to terra firma, what did you do? How did you find out exactly how they worked?
Antje - So at that time I was working a lot with isotopes. And so I had an idea, it was published by colleagues of mine who are friends today. They had an idea about metabolism. And so I tried with a suite of potential microbial food that I offered, which had radio labeling, so small amounts of radioactivity where I could measure would be eaten and taken up by the microbes consumed respired. And so I tried a lot of different things and then I found out what was expected. They cannot do this metabolism alone. They need a partner. And so when I then had the samples and looked under the microscope, this was then what put the piece together. It was not one organism that was carrying out that fascinating biochemistry. It was actually a symbiosis of two. And so that solved the problem of also why no one could find them nor cultivate them because if you have two to grow together, it's extra complicated. And so luckily they grow well in a lab and they don't necessarily need the pressure of the deep sea.
Will - So this is twice as complicated as I originally thought because there are two organisms needed in order for this process to work. As best you can to a Luddite like me, how does the actual chemistry work?
Antje - The question was if there is methane and the product of the methane consumption is CO2, which we knew it was because often these environments with these microbes, they have huge amounts of carbonate. We knew that there must be some way to bring in oxygen into the reaction, right? So you have methane, which is CH4, and you have carbonate coming out, you need a molecule that provides oxygen. And it cannot be oxygen because it doesn't exist in these sediments. So then it is obvious to an oceanographer like me, that there is a very abundant source of sulphur in the sea water. We call it sulfate. So it is S for sulphur and then oxygen in that molecule, SO4. And that is what they actually use. But to do it, they need a friend. It is a sulphate-reducing bacterium that has the right enzymes to get the oxygen from the sulphur to their buddies that want to consume methane. And thereby they do this chemistry together. The other thing that is still a bit of a mystery today. So you have two types, two entirely different types of life. They actually are in two different domains of life. So the one is a bacterium, as I said, the other one an Archaeum. And to know that the two of them, and it is exactly one species with another species, that they find each other in the sea and that they live together and that they occur everywhere globally. Just a handful of types that do this process. And they always have one counterpart. So then the question arises how do they find each other? Do they always grow together? Can we separate them? How do they transfer the electrons between them? So there's still a bunch of questions that have not been answered today. It just teaches you that life, when it has time, can develop the most amazing capacities and carry out globally relevant biochemistry. And it's life. It is some taxa that we even didn't know of before that we saw. And so we should have some respect for this amazing diversity of life that runs the planet from which we profit.
Will - Do you have any favourite theories as to how they found one another, so to speak?
Antje - Well, because it's microbes, it's cells that have no eyes, not much of sensors. They need to find each other. And so how could they? It must be surface-born recognition because there's no other way as they cannot search or signal. And so it must be on the surface. And we have made some progress with some seeing some kind of wires running from one cell to the other. You have to understand how small this life is. So the cells are a few micrometres in diameter, and the wires are then really nanowires. But we know today from also from other bacteria that bacteria can form wires and even collect energy for metals. And so potentially we have missed this ability of a single cellular life to actually tap into chemistry by forming some kind of cables or wires, really. And this is not fully researched and fully answered, but we have seen that some can produce extracellular structures with which they potentially tap into energy and also send electrons between the cells.

Antje Boetius: Why the deep sea is so important
Antje Boetius, AWI
In this edition of The Naked Scientists, deep sea microbiologist Antje Boetius explains how she discovered methane-consuming microbes, and why the seafloor is such a precious and important ecosystem...
Will - Now, as you said, these microbes convert, via chemical means, methane into carbon dioxide. And as you said, again, they are all over the world. So presumably this is a lot of methane that is getting converted.
Antje - That's exactly so. So in the very beginning when I worked on this problem a lot, I often got the question by people, is that a useful knowledge? So with that knowledge that these organisms exist, can we do something? Can we cultivate them? Can we make them eat methane from the atmosphere? Because methane is actually an aggressive greenhouse gas. It is 22 times more potent than CO2. And it is very stressful in our times where basically every gigatonne of carbon counts to know that there's so much methane leakage from the ocean, from our industry, from the cows and so on. So there was often this question to me like, can one use your microbes to control methane fluxes? So when you know these deep ocean floor microbes and when you know how slow they grow, it actually takes them months to double. Then, you know, this is not really something you can build a world's climate savings from. When you know that they live without oxygen, that they need a certain surrounding and environment and they grow better with a bit of pressure, you know, that it's actually, it's fantastic that nature has such microorganisms, but it doesn't look like they are immediately relevant to biotechnology. However, my answer was always just think about these organisms providing their services since really almost billions of years. We humans, we live on this planet not even knowing them. The planet runs the way we know it because it's of those microorganisms in the deep sea that have this job of controlling the methane. Would they not be there? And would all of that methane leak out from the ocean into the atmosphere? It would be a completely different planet. We couldn't live on it. And so my answer to why is that knowledge relevant is because it helps us understand how planet Earth functions and that this network of life of which we know not so much is essential to make the planet habitable. And so we humans, we better know who lives with us on this planet, that we don't produce mistakes, that we don't increase our risks because we have overseen that certain organisms, certain species in life are essential for the functioning of Earth, and essential for our way of living.
Will - As is so often the case in conservation, it is always best just to leave stuff alone and think better than to add to it or try and add your own. Which kind of brings us to the subject as, given you're a leading authority on the deep sea, I'm sure you're aware of the deep sea mining sort of expansions that certain countries have been looking to expand operations. Do we know what kinds of impacts this mining could have on the deep sea and therefore the sort of methane fixing that's going on?
Antje - Oh, well, in a way we could simply theoretically figure that out by understanding what resources are to be mined. Where are they, how much of the sea floor would it destroy and where and what other forms of life are living there and what is their function? So what my lab and I were studying, we were simply thinking like, what if you plug out the manganese nodule, which is one kind of a resource that in theory could deliver valuable metals, rare metals. So when you look at these manganese nodules that look like a black cauliflower <laugh>, in a way, these manganese nodules take millions of years to grow. So we could pick them only once and then they would be gone. And so when you pick them, they're a bit like when you pick up a rock from your garden, you pick up a rock and then another rock and, and on the rock is all kinds of life and insects and tubes. And so the manganese nodules themselves are kind of a home to a lot of different species. In fact, we found that some sponges in the deep sea grow only exclusively on manganese nodules and only on the sponges with some octopods lay their eggs and breed. And so again, we found so many stories about the network of life that depends on the nodules and in the intact sea floor that we found. Really, it's hard to imagine that there would be a sustainable way to take out some nodules and sea floor without destroying or harming life. And so what we do is regularly publishing our data, just alerting us of the risk that we cannot be sure that even if it's a limited area of sea floor that is destroyed, that it will not take down entire species of life because we just don't know enough. Where do they live? Are there enough around? And so that's why we find it a big risk at the time when there's so little knowledge about sea floor life. Then we also found that some of the nodules have a radioactive surface and some of the materials are toxic and the valuable metals are only a tiny percentage of these resources. And then you have to go somewhere with a lot of waste, toxic metal, maybe radioactive waste. And so the whole business case is actually also understudied and it's not clear if there would be a good business case for that. And so in many areas, we just don't have enough knowledge.
Will - Unfortunate for the deep sea, given that, as you said, it's such a slow moving process. They haven't needed to do anything quickly. They live in a dark, cold world. They've never had to encounter anything as frantic as a human being. <laugh>. They've never needed to know this sort of life where suddenly somebody could come in and tear up the entirety of the seabed.
Antje - Yeah, that's correct. So the speed of things is because it's so cold, it is slower than at the surface, which also makes the case for a whole different area of research that is super interesting. And that is really the biology of deep sea life. Now, a lot of the deep sea life forms, for example, deep sea sponges, deep sea corals, some deep sea fish, they get immensely old. And so their relatives that live in shallow water, so closer to the coast, they are not so long lived. And so there is something about life in the deep sea that is maybe slower, but also healthier because how can you be a sponge, for example I worked on arctic deep sea sponges, and get like many, many hundred years old. So we found some that are 400, 500, 600 years old, and they're healthy, reproducing, and growing really well also. And their counterparts in shallow waters, they maybe do 30 years, 40 years. That is interesting. And so for so many species in the deep sea, we still have to solve these deep biological answers. How can you be programmed to get so old? And even for the microbes, as I said, some of the microbes in the deep sea get very, very old. And that's intriguing. So is that a gene that determines how old they get? Is that biochemistry? What is it actually that some organisms are so long lived?
Will - Maybe the take home message of this really is everyone take it a bit slower and you'll live a longer, better life.
Antje - <laugh>. Yeah. And the cold helps too. Apparently, the absence of sunlight as we know might help there as well.
Will - That's a life I'm already living, so I look forward to reaching 200. One of the other things that I think I feel I have to ask and feel free to tell me this is absolute nonsense, but in terms of aerobic oxidation and methane, the early world, the early earth, was pretty hostile. Not a lot of oxygen around. How realistic is the theory that maybe the first organisms used this very mechanism?
Antje - <laugh> Yeah, that's a good question. Yes. For the longest time, Earth was anoxic. And even little amounts of oxygen got immediately consumed because there were reduced metals around and the chemistry was, you know, just sucking up any oxygen that ever emerged. However, these microorganisms, when we look at their genome and their abilities, it's super complex. So to have a suite of enzymes that allows you to break methane, activate it, and respirate with sulphate, that is a long, long list of enzymes you need. And so, as we say today, it is not imaginable that very early on we would have photosynthetic organisms because again, it's so complex to run photosynthesis. You might say the same for the methane oxidisers, that it's just too complex, all the enzymes they need to function that could not possibly be and a really early metabolism. So today we think more about hydrogen consuming microorganisms or maybe, maybe fermentors. But not really neither methanogens, nor those that make methane or those that break methane.

25:01 - Antje Boetius: The fate of polar waters
Antje Boetius: The fate of polar waters
Antje Boetius, AWI
In this edition of The Naked Scientists, deep sea microbiologist Antje Boetius explains how she discovered methane-consuming microbes, and why the seafloor is such a precious and important ecosystem...
Will - You are now, as previously mentioned, currently the director of the Alfred Wegener Institute, which operates quite heavily in polar waters, high latitude waters. What kind of research are you looking into at the moment?
Antje - I am working on a big program for Antarctica because first we have learned that the Arctic is warming so fast, four times faster than the globe on average. And Antarctica in the Southern Ocean, they were like, they always seemed a little bit like the place where everything is reliable and nothing changes. And so four or five years ago it started, however, that the Antarctic sea ice was on a rapid decline. And now we have already lost more sea ice in dimension in Antarctica compared to the Arctic. And so we have so little technology, so little infrastructure to actually understand what is going on there. I'm working with a lot of other people from many different nations on a program that we can come together to study Antarctica as we know it, to be prepared for the future. We could be that generation of people that still know the old Antarctica, and it may be gone and changed. It may be partially ice free in the summer also for centuries. And then it is our time that kind of, where I think science has duty to actually image, show, describe, learn, communicate, preserve, archive, all of that, what Antarctica is for us today.
Will - I did once, and bear with me here this does have relevance, but I was speaking to a theoretical physicist the other day who said he's worried that they're slowly going to run out of jobs because they've hit a wall in the amount that they can possibly know. I suppose that's one good thing is that you'll never have that problem.
Antje - That is true. And, we often say that we know enough to act. And of course you can also say it's also true. We know so much. And I'm always amazed when I look back into the history of climate change and the science of climate change. Like the first ones that computed the response to Earth to CO2 emissions. They were so right. They also predicted that one of the losses we will experience is the loss of sea ice. So in a way, yes, we know a lot to act, but then Earth always surprises us with different responses, with changes, with the unknown. And so I always think it's such a fantastic job that we scientists have, that we can simply help understanding how Earth and life functions and some of that knowledge is even saving lives. Sometimes this knowledge is simply there to be discovered a century later as really important and as a culture of humans as that what lives on, what remains from our times. And so I really like to think that being a scientist is of a meaning to humanity.
Will - And looking forward. As a final question, I've heard on the grapevine that you are set to become director of the Monterey Bay Aquarium Research Institute in May. What are you hoping to get done there?
Antje - Yes. So that came along a while ago. I'm actually very happy, I was very happy with my job at the Alfred Wegener Institute and the polar expeditions and all of what we did. But then parts of my studies were in San Diego and La Jolla at the Scripps Institution of Ocean Oceanography. And ever since I have a network of scientists I really admire. And many of them work and worked at MBARI. And so when they called me and asked if I could imagine applying, I immediately could picture myself at the great grand old Pacific. And working with those people that I know and being closer again to deep sea research. I mean, polar research is really important, but I also love the Pacific. I love the deep sea work and I really love to hang out in the deep sea, observe strange deep sea life. And so MBARU is the place where you get to do a kind of very free, open, innovative science because, different from other places, it is so well funded and it is actually in the DNA of the Institute, as David Packard invented it, that they are well funded and they should just experiment and try and be present at sea to deliver knowledge that no one has. And so I love that idea and I thought after working so hard, finding all the funding and doing things for the policies, why would I not have the best of all times returning to the Pacific, take a bit more time and observe.
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