, Director of the Center for Mechanisms of Evolution at Arizona State University, and Vaughn Cooper, Ph.D., professor of Microbiology and Molecular Genetics at the University of Pittsburgh, School of Medicine, examine the origins and trajectory of early microbial life (EML). They discuss the collaborative report between the American Academy of Microbiology and the Gordon and Betty Moore Foundation, which explores the journey of life on Earth, from non-living chemical compounds to early unicellular life, to the vast diversity of organisms we see today.
This episode is brought to you by the American Academy of Microbiology, a think tank at American Society for Microbiology, and the , which has been dedicated to advancing scientific discovery for the past 25 years.
Ashley's Biggest Takeaways
The origins of life have captivated the minds of scientists for ages, and what is known about the history of life on our planet is reaching unprecedented levels, thanks to advances in technology and cross-disciplinary collaboration.Incredibly, a recent meeting of the minds, facilitated by the Academy and Moore Foundation, brought together top scientists from an array of scientific disciplines to contribute knowledge to questions about early microbial life. Lynch and Cooper are the Co-Chairs of the steering committee for this project, which culminated in an over 200-page report (supported by a grant from the Moore Foundation).
I wanted to pick their brains to learn more about this work. While there is much to learn, here are some things that stood out to me:
- Understanding where life originated can be quite valuable in the field of synthetic biology.
- The origin of life can be addressed through a bottom-up or a top-down approach, but combining both is essential. These approaches are detailed on page 27 of the EML Project Report.
- Lifeforms need 1.) genetic material, 2.) metabolism, 3.) individuality to be viable.
- Getting life off the ground was a population genetics process.
- LUCA was a complicated organism; it even had phage defense systems.
- The EML project sought to convene leading-experts from a variety of scientific disciplines to help contextualize how the chemistry, geological conditions, changes in the Earth's atmosphere and environment, etc. may have influenced the probability, timing and unique processes surrounding the origin of life.
Featured Quotes:
Lynch: We're not going to know every detail. We may never understand exactly where life originated on earth, or maybe not even if it originated here, but the basic principles that are emerging are going to teach us a lot about just basic biology that applies to all organisms. So that's one way I look at it.Lynch: I think trying to understand the early starting points are also potentially quite valuable in the field of synthetic biology. So right now, synthetic biology is an interesting area, but it's all based on biology as it exists today, and there's a lot of odd things in today's cells. You probably wouldn't design certain aspects of cells if you were starting from scratch the way they are today. So, I think it really potentially opens our eyes to exploring synthetic biology with a big S—not necessarily based on current model systems, but trying to design things from scratch. And I think developing general theory will help us know what has to go down, what will work and what will not work.
Cooper: One of the things that that really struck me from the colloquia, and then in talking about what we were doing with others, was the disconnect between how we think about the origins of life. There's sort of this idea that it's this unitary event, and then everything traced from that. And so, we have all the models point to a last universal, common ancestor (LUCA). But what this program, and others like it, have pointed out is that that was in maybe the lucky one, that there were many, many alternative possibilities along the way for all of the major transitions. So, you know, that last universal common ancestor was a darn complicated microbe and that it had already figured out, in evolutionary terms, an awful lot.
Cooper: And that meant that it had been part of a pretty complicated community of diverse organisms, and you can't help but wonder what those organisms were. So, I think this program is going to help us peer more deeply into the possibilities of those unfortunate neighbors, and potentially synthesize them down the road to actually explore what they were like, and were they just unlucky or had they actually, potentially evolved in a handicapped way that prevented them from being a part of the next major transition?
Cooper: This sort of prospective synthesis can help us appreciate that there's just a lot of chance in the origin of life and, and that's both beautiful and kind of cumbersome.
Lynch: Some people are absolutely certain that there was an RNA world but I think it's open for debate, but that's okay, but that whole thought process really has gotten people thinking a lot more about RNA than people thought about before.
Lynch: We have general models in evolutionary biology that would apply all the way back to the RNA world—as long as there's a genome, these models apply. So, I think we have the capacity, if the experimentalists tell us they think this is what the setting might have been, we can use models to figure out whether it's a plausible hypothesis. It's not that different than trying to find a geological setting that seems like a plausible place for the origin of life. We ought to be able to at least say it's a plausible hypothesis for how life could have evolved and gotten off the ground. So, I think we're pretty well equipped to do that. It's just that there haven't been that many people in our field doing so. Most people in population genetics are focused on “modern-day issues” and conservation genetics and so on—rightly so—rather than these, some of these deeper issues. But I think we're really pretty well equipped to do that kind of thing.
Cooper: We know that the earth was really different during these major transitions, and there's been really significant advances in the last decade or so in models of Earth—of the chemistry, of the geological conditions, changes in the atmosphere—and how that may have influenced the probability of different timing, or even different processes of life's origin. So, you need experts who can think about that and place the emergent biological processes in the context of the environment of the Earth. That is not what we do. We also need people who are really experts in in reconstructing life's histories from genetic, genealogical models, phylogenetics. We had key people at each one of our colloquia: synthetic biologists, contemporary virologists.
Cooper: The reason why we need virologists is that the last universal common ancestor had phage defense systems, which basically means that those early life forms had parasites. So, understanding that this sort of Red Queen hypothesis of defense, counter defense, that goes all the way back, and it's shaped all of these processes.
Lynch: Thinking about origin of life hypotheses, it did start to dawn on me that we can actually start developing evolutionary theory for the origin of life. And so, I and a couple of my colleagues are starting to do that now. And it's been useful in sort of ground truthing some of the ideas that have been thrown around. And we're a lot farther than we were 20 or 30 years ago in origin of life.
Lynch: My personal view is that the mitochondrion isn't that kind of energetic savior that some people would like to think it is it, but on the other hand, we're stuck with the mitochondria, that's how we make our energy today.
Cooper: We owe all of our replication machinery—DNA replication—to archaea. But we have bacterial-like membranes, and then, obviously, we have properties endowed by the mitochondria, which was a bacteria. So we are hybrids. I like to think it's sort of an inclusive entity that represents all of microbial life. And I think it's then appropriate for these studies to be welcomed back and motivated by the community of microbiologists.
Links for This Episode:
- Project Report Early Microbial Life: Our Past, Present and Future.
- Article: The Great Oxidation Event: How Cyanobacteria Changed Life.
- MTM Podcast: From Hydrothermal Vents to Cold Seeps: How Bacteria Sustain Ocean Life With Nicole Dubilier.
- Take the