According to the researchers, the hypothesis that viruses were necessary for the evolution of humans and other complex
There is a well-established idea that all complex life forms, such as humans, starfish and trees, arose when archaea and bacteria merged to form a hybrid organism.
Recent studies show that the firsteukaryotes are direct descendants of the so-called Asgardian archaea. Now the authors of the new work said that viruses could also play a role in this story.
The authors found viruses that infect living Asgard archaea. Archaea are unicellular microorganisms that do not have a nucleus or any membrane organelles.
The viruses found have some similarities withviruses that infect eukaryotes, in particular, can copy their DNA and take over protein modification systems. The fact that these reconstituted viruses share characteristics of both eukaryotic and prokaryotic viruses makes them unique. They're not quite like what infects other archaea or complex life forms.
Asgardian archaea likely evolved over 2billion years ago. And their descendants are still alive: they are found in deep-sea sediments and hot springs around the world, but so far only one strain has been successfully grown in the laboratory.
To identify them, scientists collectgenetic material from the environment and then accumulate genomes. The authors scanned the Asgard genomes for the presence of repetitive DNA segments - they contain small fragments of viral DNA. Further, they were able to accurately compare with the viruses that infect organisms that play a key role in the complex history of the origin of eukaryotes.
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