It has been discovered for the first time that viruses can infect a class of bacteria that may encompass the origins of all complex life.
The finding provides intriguing hints regarding the beginnings of complex life and promotes fresh lines of inquiry into the idea that viruses were crucial to developing life forms like humans and other animals.
The University of Texas at Austin researchers published their work, "Genomes of six viruses that infect Asgard archaea from deep-sea sediments," in the journal Nature Biology.
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Group of Microbes Play a Role in the Evolution of Asgard Archaeans
All complex life forms, including people, starfish, and trees (which have cells with a nucleus and are referred to as eukaryotes), are thought to have formed when archaea and bacteria mated to create a hybrid creature. This theory is highly accepted. According to recent findings, the earliest eukaryotes are the direct offspring of the Asgard archaea.
The most recent study, conducted by Brett Baker's lab and Ian Rambo, a former doctorate student at UT Austin, gives insight into how viruses may have also contributed to these billions of years old history.
"This study is opening a door to better resolving the origin of eukaryotes and understanding the role of viruses in the ecology and evolution of Asgard archaea," Rambo said per Phys.org. "There is a hypothesis that viruses may have contributed to the emergence of complex cellular life," he added.
Rambo is alluding to the controversial theory of viral eukaryogenesis. It implies that viruses, in addition to bacteria and archaea, may have contributed a genetic component to the eukaryotic genesis. The most recent finding provides some intriguing hints but does not resolve that controversy.
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Evidence of Virus' Significance in the Evolution of Life
The recently identified viruses that infect presently thriving Asgard archaea have certain characteristics to viruses that infect eukaryotes, such as the capacity to duplicate their own DNA and use their hosts' protein modification mechanisms.
These recovered Asgard viruses differ from viruses that infect other archaea or sophisticated living forms. They exhibit traits of both viruses that infect eukaryotes and prokaryotes, which have cells without a nucleus.
"The most exciting thing is they are completely new types of viruses that are different from those that we've seen before in archaea and eukaryotes, infecting our microbial relatives," said Baker, associate professor of marine science and integrative biology and corresponding author of the study in a statement.
Around the planet, deep marine deposits and hot springs have yielded the Asgard archaea, which most likely formed more than 2 billion years ago and whose descendants are still alive. However, only one strain has so far been successfully produced in a lab. Scientists gather their genetic material from the environment and combine their genomes to identify them.
In this most recent investigation, scientists searched the Asgard genomes for repetitive DNA sequences called CRISPR arrays, which contain minute fragments of viral DNA that can be accurately linked to viruses that have previously infected these bacteria. They were able to recognize these sneaky viral invaders, which affect creatures important to the intricate creation narrative of eukaryotes, thanks to their genetic "fingerprints."
The implications and potential significance of viruses in the eukaryogenesis enigma are now beginning to be understood, according to co-author of the paper Valerie De Anda, a research associate at UT Austin.
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