Astrobiologists Expand Knowledge Of Virus Diversity

Astrobiologists supported by NASA have completed a study of RNA viruses on Earth and have vastly expanded knowledge of virus diversity. Currently, there are thought to be five broad categories (phyla) of viruses.

The team of scientists developed a computational method that allows for the sensitive detection of RNA viruses, and then studied genetic sequences by examining the RNA from over 5000 viruses. In this genetic information, they identified over 2.5 million RNA virus contigs. Contigs are small sections of a genetic sequence that overlap, and by fitting lots of these little pieces together you can reconstruct the original, complete sequence of genetic information. You can also compare which contigs are present in different individual viruses to get a picture of how the viruses are related, and how different groups of viruses have evolved over time.

The findings reveal that the diversity of RNA viruses on Earth is at least five times larger than previously recorded. The results support the idea that there are five phyla of viruses, but the team also proposes that a sixth phylum should be added. This new phylum would be RNA viruses that make a certain type of protein that can break cell membranes (a lysis protein). Additionally, the team identified other, previously unknown, types of proteins that could play a role in how viruses interact with and infect cells.

The team also discovered that a small cluster of RNA viruses is specifically associated with a bacterium (Roseiflexus sp. RS-1) from hot springs in Yellowstone National Park. This is the first time that this group of RNA viruses had been shown to be associated with a bacterial host. Previously, these viruses were only known to use eukaryotes as hosts.

Viruses are abundant on Earth and may have played an important role in the origin and evolution of life as we know it. Some theories predict that viruses have coexisted with cellular organisms since the beginning of life on our planet.This makes understanding viruses, the way they work, and their diversity in the environment important in the search for habitable environments beyond our planet.

The study, “Expansion of the global RNA virome reveals diverse clades of bacteriophages,” was published in the journal Cell.

Astrobiology, genomics,