Viral dark matter: a potential weapon against climate change

Several of the 5,500 marine RNA virus species recently discovered by scientists could help push carbon absorbed from the atmosphere into permanent storage on the ocean floor, according to a study.

The findings also show that a small number of these newly discovered species have “borrowed” DNA from the infected animals, which could help researchers determine their putative hosts and functions in marine processes.

A better understanding

The research leads to a better understanding of the excessive impact these tiny particles have on the ocean environment, in addition to mapping a wealth of ecological key data.

“The findings are critical for building models and anticipating what will happen to carbon in the right direction and at the right scale,” said Ahmed Zayed, co-first author of the paper and a research scientist in microbiology at the University of Groningen. Ohio State University.

When considering the immensity of the ocean, the topic of size is a critical concern.

Ohio State University professor of microbiology Matthew Sullivan expects to discover viruses that, when created on a large scale, could act as programmable “buttons” on a biological pump that controls how carbon is deposited in the ocean.

“We are becoming increasingly aware that we may need to adjust the pump on an ocean scale,” he said. Sullivan says society relies on that technological cure, but is a challenge to solve.

Science published the study online.

Also read: Data shows carbon dioxide levels hit record high

assess damage

(Photo: KARIM SAHIB/AFP via Getty Images)

These RNA viruses were discovered in plankton samples collected by the Tara Oceans Consortium, a global study of the impact of climate change on the ocean aboard the schooner Tara. The international effort aims to learn more about the mysterious organisms that live in the sea and do most of the work by absorbing half of the human-generated carbon in the atmosphere and producing half of the oxygen that we breathe in to predict how the ocean will respond to climate change.

While these marine viral species are not harmful to humans, they function like all viruses, infecting another being and using its cellular machinery to replicate itself. While the consequence can always be dangerous to the host, the actions of a virus can have environmental benefits, such as helping to spread a toxic algal bloom.

Key to determining their place in the ecosystem has been the development of computational approaches that can extract information about RNA virus activities and hosts from small genome segments according to genomics standards.

Guillermo Dominguez-Huerta, a former postdoctoral researcher in Sullivan’s lab, noted, “We’ll let the data guide us.”

The team used statistical analysis of 44,000 sequences to classify RNA virus communities into four ecological zones: Arctic, Antarctic, temperate, and tropical epipelagic (closest to the surface, where photosynthesis occurs), and temperate and tropical mesopelagic (most relative to the surface). surface, where photosynthesis takes place) (200-1,000 meters deep). These zones are similar to the zone designations for the nearly 200,000 marine DNA virus species previously found by the researchers.

There were some unexpected results. While biodiversity tends to increase near the equator and decrease near the poles, Zayed said a network-based study of ecological interaction revealed that the diversity of RNA virus species in the Arctic and Antarctic was greater. than predicted.

“Viruses don’t care about temperature when it comes to variation,” he says. “The wide variety we see in polar locations is great because we have more viral species competing for the same host. We observe fewer host species, but more viral species infecting the same animals,” said the researcher.

Identify hosts

To identify potential hosts, the researchers used a combination of methods, first inferring the host from the viruses’ categorization in the context of marine plankton and then generating predictions based on how the virus and host quantities “co-vary”. as their abundances depend on each other. Finding evidence of RNA virus incorporation into cellular genomes was the third technique.

“The viruses we’re investigating don’t add themselves to the host genome, but many do so by accident, which is a hint about the host, because if you detect a viral signal in a host genome, it means the virus is inside the cell. was at one point,” Dominguez-Huerta explained.

While most dsDNA viruses infect bacteria and archaea, which are widespread in the ocean, this recent study found that RNA viruses mainly infect fungi and microbial eukaryotes and invertebrates to a lower level. Only a small percentage of marine RNA viruses can infect bacteria.

The researchers also discovered 72 different functionally distinct supportive metabolic genes (AMGs) spread across 95 RNA viruses. These provided some of the best clues about what kind of organisms these viruses infect and what metabolic processes they are trying to reprogram to maximize the “manufacture” of viruses in the ocean.

Further research

Further network-based research discovered 1,243 RNA virus species associated with carbon export, 11 of which are suggested to be active in facilitating carbon export to the ocean floor. Two viruses associated with algal hosts were chosen as the most promising targets for further research.

“We’re getting to the point where we can create metabolic maps from pockets of genes,” said Dr. Richard Sullivan, associate professor of biogeosciences.

Sullivan, Dominguez-Huerta and Zayed are members of the EMERGE Biology Integration Institute in the state of Ohio.

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