Asgard archaea may reshape understanding of eukaryotic evolution

Researchers have made significant discoveries about Asgard archaea, a recently identified group of microorganisms. This study helps explain how life on Earth may have evolved. It was published in the journal Cell by scientists from ETH Zurich. Asgard archaea were first discovered in 2015 near an underwater volcano called Loki. Researchers found gene fragments in deep-sea sediments that pointed to this new type of microbe. After analyzing these fragments, they were able to piece together the complete genome of Asgard archaea. The name "Asgard" comes from Norse mythology, reflecting the microbes' discovery site near a location known as Loki's Castle. Similar to bacteria, Asgard archaea consist of single cells, but they differ in their genetic makeup and metabolic processes. Microtubules, which play a role in cell transport and division, are important in this research. In eukaryotes, these structures are essential for cell functions. The study suggests that microtubules in Asgard archaea could have advanced their development and contributed to the evolution of more complex cells. Using advanced microscopy, researchers found a protein in Asgard archaea called Lokiactin. This protein forms structures similar to the cytoskeleton found in eukaryotic cells. Unlike other proteins, tubulin appears in only a few Asgard archaea species. The study indicates that the origin of microtubules may be linked to Asgard archaea, which might have allowed these organisms to capture and engulf bacteria. Over time, this interaction led to the development of mitochondria—the energy producers in modern cells. There is growing belief that eukaryotes may have emerged from Asgard archaea. Researchers propose that eukaryotes could be considered a subgroup within Asgard due to genetic similarities. This challenges the traditional classification of life into three domains—bacteria, archaea, and eukaryotes—suggesting a reduction to just two: archaea (including eukaryotes) and bacteria. The team, led by researcher Pilhofer, is eager to learn more about Asgard archaea and their connection to eukaryotes. They emphasize that many questions remain about the biology of these unique microbes and their role in evolutionary history.