Sunday , July 25 2021

An expedition around the world finds 200,000 types of viruses in the oceans

Tara floating in the Arctic.
Photo: Tara Ocean

After exploring the ocean from pole to pole, scientists have discovered nearly 200,000 marine virus populations.

In the marine ecosystem, small living creatures, called microbes, make up the bulk of the ocean's biodiversity and over half of its biomass. But much less is known about viruses – genetic information packets that reproduce in other living creatures – that exist in the oceans. Scientists have begun to explore the marine viral community, its diversity and its function, especially how it affects microbes. On Thursday, they announced the creation of a huge global catalog of marine viruses, which marks an important step in answering many of these questions.

"Expands our knowledge of what the biological beings of our planet are," said Ann Grigory, author of a study and post-doctorate at VIB-KU Leuven in Belgium.

The data comes from 146 samples taken on several expeditions on board the Croatian Tara, including 41 trips from 2013 to the Arctic Ocean. Researchers must first determine whether the genetic material in the sample is viral or not, with different bioinformation tools comparing it to known viruses, said co-author Ahmed Zayed, a student at Ohio State University. They then compare the strands of DNA with each other to divide them into viral populations.

The analysis revealed 195,728 virus populations, 12 times the previous analysis of a smaller set of data, according to a report published in Cell. It has been more closely understood that these populations appear to be stacked in five meta-communities that researchers call ecological zones: the Arctic; Antarctica; deeper than 2000 meters; 150-1000 meters; and moderate / tropical waters with a depth of 0 to 150 meters. Perhaps surprisingly, latitude does not provide for viral diversity.

This is an exciting job. Microbes are perhaps the key engines of biochemical processes in the ocean, and microbes are infected with viruses. "I think people know that viral diversity far exceeds that of huge microbial diversity," said Allison Buchan, a professor at the University of Tennessee, Knoxville. "But there has not been a large number of studies that have attempted to determine the extent of this diversity."

What do you do with such a large set of data? Most of all, you're exploring it to try to better understand the roles of all these viruses. Similar to how rabies virus can increase the aggression of the infected animal to facilitate transmission, perhaps some of these viruses are important to chemical processes in the ocean. Many of them also lead to the death of microbes. And perhaps this huge new stock of genetic information contains something that will be useful to people.

"Maybe you can dig it for new genes," Gregory said. Let the researchers discover new antibiotics that use this genetic information.

This data set is certainly not exhaustive, Gregory and Zayed warn. It only includes viruses that contain DNA, not those containing RNA (somewhat simple, the DNA is composed of a pair of complementary strands of genetic material, whereas the RNA consists of one strand). Bukan also noted that this was rather a snapshot. Six months later, they may have gathered different results, she said.

This study is a great reminder that as we know about Earth's life, the oceans remain filled with unknowns.

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