The origin of life: How the microbes laid the foundation for complex cells

With computer aid, researchers assembled these fragments like a piece of puzzles to compile the whole genome. Only then did they realize that they were dealing with the previously unknown group of Archae.

Like bacteria, Archaea are one -cellar organisms. Genetically, however, there are significant differences between two domains, especially in terms of their cell envelopes and metabolic processes.

After further searching, microbiologists identified appropriate organisms, described and classified them as a separate archeal subgroup: Asgard Archaea. Their name, taken from the celestial empire in Norwegian mythology, points to their initial discovery near Loki’s castle-black smoker at the Middle Actral Greben between Norway and Svalbard.

In fact, Asgard Archaea appeared almost the sky sent to research: it was shown that there were a missing connection between Archae and Eukariota-that is, between the archae and organisms whose cells contain a nucleus, such as plants and animals.

A tree of life with one branch less

In recent years, researchers have discovered the increasing indications of close relationships between Asgard Archae and Eukariot, and that the latter may develop from the first. The division of all living organisms into three domains of bacteria, Archae and eukaryota did not stay for this surprising discovery.

Some researchers have since suggested eukariota as a group within Asgard Archae. This would reduce the number of living domains from three to two: Archaea, including eukaryotes and bacteria.

In Eth Zurich, Professor Martin Pilhofer and his team were fascinated by Asgard Archae and examined mysterious germs for several years.

In an article published in Nature Two years ago, researchers ETH explored the details of cellular structure and architecture Lokiarchaeum ossiferum. Originally from the sediment of the side water channel in Slovenia, this Asgard Archaeon was isolated by researchers in the Laboratory of Christian Schleper at the University of Vienna.

In this study by Pilhofer and his postdoctoral researchers Jingwei Xu and Florian Wollweber showed that Lokiarchaeum ossiferum owns certain structures also typical of eukaryotes. “We have found a protein of actin in this species that seems very similar to the protein found in eukaryots – and occurs in almost all Asgard Archae discovered to this day,” Pilhofer says.

In the first study, the researchers combined different microscopy techniques to show that this protein-tasted lociactin-formation of fibrous structure, especially in numerous protrusions of thousands of thousands of thousands of. “They seem to form a skeleton for complex cell architecture of Asgard Archaea,” adds Florian Wollweber.

In addition to actin philanames, eukaryots also have microtubules. These pipe -shaped structures are the second key component of the cytoskeleton and consist of numerous tubulin proteins. These tiny pipes are important for transport processes inside the cell and segregation of chromosomes during cellular division

The origin of these microtubules has been unclear so far. In a newly published article in Cell ETH researchers discovered related structures in Asgard Archae and described their structure. These experiments show that Asgard tubulins form very similar to microtubules, although less than those in their eukaryotic relatives.

However, only a few Lociarchaeum The cells form these microtubules. And, unlike actin, these proteins of tubulin appear only in very few types of Asgard Archaea.

Scientists do not yet understand why tubulins rarely appear in Lokiarchae or why cells are needed. In eukariots, microtubules are responsible for transport processes within the cell. In some cases, motor proteins “walk” these pipes. ETH researchers have not yet noticed such motor proteins in Asgard Archae.

“However, we have shown that pipes formed from these tubulin are growing at one end. Therefore, we doubt that they perform similar transport functions as well as microtubules in eukaryotes,” says Jingwei XU, Sui-Book Author Cell study. He produced tubulin in cellular culture with insect cells and examined their structure.

Researchers in the field of microbiology, biochemistry, cell biology and structural biology have closely collaborated in the study. “We would never progress so far without this interdisciplinary approach,” emphasizes Pilhofer with the degree of pride.

Was the cytoskelets key to developing a complex life? Although some questions remain unanswered, the researchers are convinced that the cytoskeletal has been an important step in the evolution of eukaryota.

This step could happen before Aeon, when Asgard Archaeon crept a bacterium with his accessories. During evolution, this bacterium developed into a mitohondrion, which serves as the power of modern cells. Over time, core and other sections developed – and a eukaryotic cell was born.

“This extraordinary cytoskelet was probably at the beginning of this development. He could have enabled Asgard Archae to form supplements, allowing them to communicate, then take away and take a bacteria,” Pilhofer says.

Asgard Archaeae fishing

Pilhofer and his colleagues are now planning to draw attention to the function of actin philaments and archeal tubulin along with the resulting microtubule.

They also aim to identify the proteins discovered by the researchers on the surface of these microbes. Pilhofer hopes his team will be able to develop antibodies accurately adapted to these proteins. This would allow researchers to “fish” especially for Asgard Archae in mixed microbes cultures.

“We still have many unanswered questions about Asgard Archae, especially regarding their relationship to eukaryots and their unusual cell biology,” Pilhofer says. “Monitoring the secrets of these microbes is fascinating.”