Asgard Archaea May Hold the Key to the Origins of Eukaryotic Life

A group of single-celled organisms known as Asgard archaea has drawn scientific attention for its potential link to the evolution of complex life. These microbes were first identified through gene fragments in deep-sea sediments. They have been recognised as a separate archaeal subgroup. Their discovery has led to significant questions about the classification of life forms. Researchers suggest that eukaryotes, organisms with a nucleus, may have evolved from these microbes. This challenges the long-standing three-domain model of life that separates bacteria, archaea, and eukaryotes.

Findings from Recent Studies

According to a study published in Cell, researchers at ETH Zurich have examined the cellular structure of Asgard archaea, particularly Lokiarchaeum ossiferum. The study, led by Professor Martin Pilhofer, highlights the presence of an actin protein called Lokiactin. This protein is similar to actin found in eukaryotic cells and forms filamentous structures, which are believed to contribute to the microbes’ complex architecture. Postdoctoral researchers Jingwei Xu and Florian Wollweber conducted microscopy studies to confirm the role of these structures.

Microtubules in Asgard Archaea

In an earlier study, the team identified actin filaments in Asgard archaea, but the presence of microtubules had remained uncertain. The latest findings reveal that Asgard archaea produce tubulin proteins that form microtubule-like structures, though on a smaller scale than those in eukaryotic cells. Unlike actin filaments, these tubulins were observed in only a few species. Their function is not fully understood, but researchers suggest that they might support transport within the cell.

Implications for Evolutionary Biology

According to reports, the cytoskeleton of Asgard archaea may have played a crucial role in the emergence of eukaryotic life. Scientists propose that an Asgard archaeon could have engulfed a bacterium, which later evolved into mitochondria. Pilhofer stated in Cell that these cytoskeletal structures may have enabled interactions between archaea and bacteria, ultimately leading to the development of eukaryotic cells. Research into these microbes continues, with efforts focused on understanding their proteins and cellular functions.