According to this latest study, all complex life forms (a.k.a. eukaryotes) trace their roots back to a common ancestor among a group of microbes called the Asgard archaea.
Newswise — In a groundbreaking discovery reported in the prestigious journal Nature, it has been revealed that Thor, the renowned Norse god hailing from the mythical city of Asgard, is not the sole inhabitant of his realm. Astonishingly, this research indicates that we humans, along with a multitude of diverse organisms such as eagles, starfish, daisies, and every other complex life form found on Earth, can be likened to Asgardians in a certain context.
Recent research conducted by The University of Texas at Austin, in collaboration with other institutions, has delved into the genomes of various archaea microbes, leading to a significant discovery. The study reveals that eukaryotes, which encompass complex organisms with nuclei in their cells, including plants, animals, insects, and fungi, can be traced back to a shared ancestor within the Asgard archaean lineage. This finding establishes eukaryotes as a distinct and interconnected group, analogous to birds being one subset within the broader category of dinosaurs, as they both share a common ancestor. Remarkably, the research team has determined that all eukaryotes can be traced back to a common Asgard ancestor, highlighting their evolutionary interconnectedness.
No fossils of eukaryotes have been found from farther back than about 2 billion years ago, suggesting that before that, only various types of microbes existed.
Brett Baker, an associate professor of integrative biology and marine science at UT Austin, pondered the events that drove the evolution of microbes into eukaryotes. Reflecting on the magnitude of this question, he emphasized the significance of uncovering a common ancestor as a crucial milestone in unraveling the mysteries behind this transformation.
Thijs Ettema from Wageningen University in the Netherlands, along with his research team, made a significant discovery in their pursuit. They identified a newly described order known as the Hodarchaeales (or Hods for brevity), which serves as the closest microbial relative to all complex life forms on the tree of life. These remarkable organisms, found in marine sediments, belong to the larger group of Asgard archaea, with the Hods representing one of several subgroups within this classification.
More than 2 billion years ago, the Asgard archaea underwent their evolutionary journey, and their descendants continue to thrive today. While researchers have detected certain Asgard archaea strains in deep sea sediments and hot springs worldwide, only two strains have been successfully cultivated in laboratory settings thus far. To identify these organisms, scientists gather their genetic material from the surrounding environment and painstakingly assemble their genomes. By comparing the genetic similarities with other organisms that can be grown and studied in the lab, scientists can make educated inferences about the metabolic processes and other characteristics exhibited by the Asgard archaea.
Valerie De Anda, a researcher in Brett Baker's laboratory, evokes the concept of a time machine that transcends the exploration of dinosaurs or ancient civilizations. Instead, she envisions a journey into the depths of metabolic reactions that might have ignited the emergence of complex life. In this unique quest, rather than relying on fossils or ancient artifacts, the researchers delve into the genetic blueprints of contemporary microbes, employing them as a crucial resource to reconstruct the past and unlock the mysteries of our evolutionary history.
Through their work, the researchers made significant strides in broadening the understanding of Asgard genomic diversity. They incorporated over 50 previously unknown Asgard genomes into their modeling efforts. The analysis yielded intriguing insights, suggesting that the common ancestor of all modern Asgard archaea thrived in hot environments and relied on consuming CO2 and chemicals for sustenance. In contrast, the Hods, which share a closer evolutionary relationship with eukaryotes, exhibit metabolic similarities to humans by consuming carbon-based sources. Furthermore, Hods are found to thrive in cooler environments. These findings shed light on the diverse metabolic strategies employed by different branches of the Asgard archaea and provide valuable clues about their ancient origins and adaptations.
“This is really exciting because we are looking for the first time at the molecular blueprints of the ancestor that gave rise to the first eukaryotic cells,” De Anda said.
In Norse mythology, Hod (also spelled Höd, Höðr or Hoder) is a god, the blind son of Odin and Frigg, who is tricked into killing his own brother Baldr.
“I keep joking in my talks that ‘We are all Asgardian’,” Baker said. “Now that’s probably going to be on my tombstone.”
Additional authors from UT Austin include Kiley W. Seitz and Nina Dombrowski. Apart from Ettema, researchers from other institutions who contributed to the study are Laura Eme, Daniel Tamarit, Eva Caceres, Courtney Stairs, Max Schön, William Lewis, Felix Homa, Jimmy Saw, Jonathan Lombard, Takuro Nunoura, Wen-Jun Li, Zheng-Shuang Hua, Lin-Xing Chen, Jillian Banfield, Emily St. John, Anna-Louise Reysenbach, Matthew Stott, Andreas Schramm, Kasper Kjeldsen, and Andreas Teske.
This research received support from various sources, including the Origin of Eukaryotes program at the Moore and Simons Foundations, the U.S. National Science Foundation, the Wellcome Trust Foundation, the European Research Council, the Swedish Research Council, the Dutch Research Council, the National Natural Science Foundation of China, the Wenner-Gren Foundation, the Science for Life Laboratory in Sweden, and the European Commission's Marie Skłodowska-Curie Actions.
Baker expressed his enthusiasm, stating, "What I find most thrilling is the emergence of Hodarchaeales as an organism that bears resemblance to a eukaryote rather than an archaeon, as traditionally believed by biologists. In essence, these Hods can be regarded as our evolutionary cousins within the realm of archaea."
Baker noted that it is logical for the Asgard archaea, out of all known archaeal groups, to have given rise to eukaryotes. This is due to the fact that, similar to eukaryotes, Asgard archaea possess numerous genes with multiple copies within their genomes. In eukaryotes, the duplication of genes frequently led to the acquisition of new functions by the duplicated copies, thereby equipping organisms with novel abilities. This phenomenon played a significant role as a driving force in evolution.
Baker clarified that the specific outcomes of gene duplications within the Asgard archaea are not yet known. However, based on our understanding of eukaryotes, it is evident that gene duplications contributed to the emergence of new functions and a greater level of cellular complexity. Therefore, it is speculated that similar gene duplications within Asgard archaea played a crucial role in driving the evolutionary innovations that ultimately defined eukaryotes.
Researchers examining archaea have made a remarkable discovery of numerous proteins previously believed to be unique to eukaryotes. This revelation has led Baker to pose an intriguing question: What roles do these eukaryotic proteins fulfill within the archaea?
“I think studying these simpler forms of life and their eukaryotic characteristics is going to tell us a lot about ourselves,” Baker said.
RSS