This link is crucial in understanding how complex organisms, such as humans and plants, evolved from microbes. Scientists have long been puzzled by this mystery. The fundamental building blocks for all life, cells are. Although microscopic organisms such as bacteria, viruses, and microbes, are composed of simple cells only, visible life is made up of complex and large cell types. Complex cell types have been difficult to identify for scientists. There has always been a missing link. Researchers from Uppsala University, Sweden and their colleagues from Norway and Austria have now found the solution. They discovered a new class of microorganisms that represent the missing link to the evolution from simpler cells to more complex ones. Scientists think that “Loki” is the missing link in Earth’s evolution from simple to complex life forms. The 1970s was where Carl Richard Woese (1928-2012), an American microbiologist/biophysicist, discovered a new class of microorganisms: the Archaea. These were a new realm or Kingdom of Life, a distinct branch of the Tree of Life. This discovery stunned scientists at that time. Although archaeal cells are small, simple, and resemble bacteria, scientists discovered that Archaea was closely related to “eukaryotes”, organisms with complex cell types. Humans, for example, are eukaryotes. Biologists have struggled for decades to understand how complex cell types in eukaryotes emerged from Archaea cells. Thijs Ettema (Department of Cell and Molecular Biology), Uppsala University) and his colleagues from the Universities of Bergen (Norway) wrote about the discovery of a new Archaea group, called the ‘Loki. This is shorthand for Lokiarchaeota. It is believed to be the missing link in the evolution of eukaryotes. Dr. Ettema is the team leader. He said that the puzzle surrounding the origin of eukaryotic cells is very complicated because many of its pieces remain missing. Although we hoped Loki would provide more information, the results were overwhelming. It was simply stunning.” We studied its genome and found that Loki is an intermediate type in between the microbe-like cells and complex cells of eukaryotes. This was confirmed by Loki being placed on the Tree of Life. Lionel guy from Uppsala University was also a co-author. He said that Loki made a strong group with the eukaryotes. Anja Spang (a researcher at Uppsala University’s Department of Cell and Molecular Biology) said that Loki shared many genes with eukaryotes. Loki is located near the Arctic Mid-Ocean Ridge. (Image: R.B. Pedersen University of Bergen. Lokiarchaeota is named after the hostile area it found – Loki Castle – a hydrothermal system that lies in the Mid-Atlantic Ridge, between Norway and Greenland at 2 ,353 meters below the ocean surface. Steffen Jorgensen is a Norwegian researcher who studies at University of Bergen. He said that hydrothermal vents, which are volcanic systems, can be found at the ocean’s floor. Loki’s location is highly influenced by volcanic activity but it actually has a low temperature. Jimmy Saw from Uppsala University’s Department of Cell and Molecular Biology said that extreme environments often contain a lot of unknown microorganisms. This we call microbial darkness matter. Dr. Ettema and his colleagues are hoping to learn more about how complicated cells developed. We are only just beginning. There is still a lot out there to discover, and I am convinced that we will be forced to revise our biology textbooks more often in the near future”, said Dr. Ettema.” Citation: “Complex archaea that bridge the gap between prokaryotes and eukaryotes,” Anja Spang, Jimmy H. Saw, Steffen L. Jorgensen, Katarzyna Zaremba-Niedzwiedzka, Joran Martijn, Anders E. Lind, Roel van Eijk, Christa Schleper, Lionel Guy & Thijs J. G. Ettema. Nature. Published May 6, 2015. DOI: 10. 1038/nature14447.
