Entirely new virus family found in the oceans

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A team of researchers have announced the discovery of a new group of viruses in the world’s oceans. Remaining elusive until now, this virus group play a major role in bacterial regulation. It is also possible that it is not contained merely to the oceans.

The ocean is crowded: no less than 10 million viruses can be found in just one millilitre of water. Although the majority of these are well known, there are others that remain out of our grasp. Or at least they did until now. A team of microbiologists have in fact announced the discovery of a previously unknown virus family which dominates the ocean, and which could not previously be detected by standard laboratory testing. The researchers suspect that this virus family could also evolve outside of the oceans, and possibly even inside our bodies.

“We don’t believe that it is exclusive to the ocean”, explains environmental microbiologist Martin Polz, from Massachusetts Institute of Technology (MIT). The researchers analysed three months worth of water samples taken from the ocean off the coast of Massachusetts. They succeeded in isolating and studying specimens of this virus, which constitutes a missing link in the evolution of viruses, playing an important role in the regulation of bacterial populations. What they found floating in the water is equally remarkable for the fact that these viruses do not appear to resemble any others.

According to the researchers, the most abundant viruses in the planet are double-stranded DNA (dsDNA) viruses, of which the “tailed” variety (Caudovirales) is the best known. There is much less known about the tail-less specimens in question here, mainly because their biological characteristics are not easily detected by standard tests. However, researchers have now succeeded in detecting them, and have also been able to sequence their DNA. They have named this new group “Autolykiviridae”, after Atolycos, a character from Greek mythology known for being difficult to catch.

These tail-less viruses appear to be representative of an ancient viral line defined by specific types of capsid -the protein shell that surrounds DNA viruses. These frequently infect animals and unicellular organisms, but not bacteria. The genomes of this new virus family are very short compared to tailed viruses, being composed of around 10,000 bases in comparison to 40,000 or 50,000 in general for tailed viruses. Additionally, while the majority of viruses attach to only one or two types of bacteria, it appears that these can infect dozens of different types, suggesting that they play an enormous role in terms of regulation of bacterial life in the ocean. Veritable microscopic predators.

This ruthless efficiency may not be limited to the ocean, as this new virus group in fact appears to be particularly widespread. The researchers suggest that we could even find it in the human microbiome. In fact, by sifting through DNA databases, to see if scientists had previously studied any similar viruses, the stomach showed up in the results. Further research will be necessary to develop our understanding of the implications of this virus -whether in the ocean or in other ecosystems.

The results of this study are reported in Nature.