You don’t eat any virus, right? Meet hungry protists

There is a true buffet of viruses on the planet Earth dinner plate — Amount of biomass That’s about 25 billion people.

Therefore, it may be a little confusing that scientists have not yet identified the species that are deliberately eating the virus for energy.

However, increased evidence suggests that at least one group of organisms can affect nutrient-rich viruses: protists that scientists struggled to put in the tree of life, microscopic. , And often unicellular organisms. Like viruses, protists are expected to be in billions of trillions of seawaters-some may swallow marine viruses, according to a study published in the journal Thursday. Microbiology Frontier..

If the findings are successful, they can help reverse the doctrine of centuries ago. Instead of acting only as a chaos pathogen and drowning out life, the virus can play a role in promoting and maintaining it in some cases.

New studies alone cannot reveal a consumptive link between protists and viruses, said Rika Anderson, a microbial ecologist at Carlton University in Minnesota who was not involved in the study. However, protists have been found in tremendous habitats, from rotten tree stumps to animal intestines, and may have evolved at least many strategies to feed themselves. there is.

“They are eating all sorts of things,” Dr. Anderson said. “I wouldn’t be surprised if the virus was consumed.”

The team, led by Ramnas Stepanauscus, a microbial ecologist at the Bigelow Institute for Marine Sciences in Maine, started the project over a decade ago. They initially intended to study the prey preferences of marine protists, many of which stopped bacteria.

“The current doctrine is that protists eat other single cells,” said Dr. Stepanauscus.

Researchers collected seawater samples from the Gulf of Maine and the Mediterranean and selected about 1,700 protists. Then I opened the cells one by one, split them, and analyzed their contents. The genetic material different from that of the protists inferred by the team was probably a sign of what the microbes ate.

However, after repeated analyzes, the researchers were surprised and disappointed that there weren’t too many bacterial substances to disappoint. Instead, there were viruses of all shapes and sizes, sometimes attacking dozens of cells. Protists from two groups, choanozoa and picozoa, were never found in their cell freight without viral genes.

Julia Brown, a microbiologist at the Bigelow Institute and the lead author of the study, said this was a strange discovery. But as far back as the 1990s, researchers positive It Some protist species I may be able to do it of Joint selection Virus For food..

In some early experiments, Dr. Brown said researchers slurried the two microorganisms together in the laboratory to see if the protist would consume and digest the virus. However, despite promising results, this series of studies has received little attention for years since then. “It just fell off the map,” she said.

Dr. Brown said genetic experiments examining one cell at a time may help enhance the case of virus consumption. Because they can show what the protists ate under natural conditions. “We can catch them no matter what they are doing,” she said. Technologies that are accurate enough to achieve this have only recently begun to be used.

“This is a particularly great technical feat they have separated,” said Rosie Alegado, a microbial oceanographer at the University of Hawaii at Manoa, who was not involved in the study.

Still, finding the genetic material of the virus inside or around the cell does not mean that the virus was once lunch. For example, some viruses may have infected the protist or simply attached to the surface of the cell.

However, Dr. Brown and Dr. Stepanauskas said that certain viruses were found only in certain groups of protists, implying that the interaction was not just a coincidence. And many of the identified viruses are thought to be capable of infecting only bacteria, not protists.

Another possibility is that the virus was infected with a bacterium and then swallowed by a protist, creating a type of microorganism, Tardolken. However, the viral and bacterial genetics were not always tracked together, Dr. Brown said, implying that some protists may have skipped mediators and went straight to the viral virus.

Henry N. Williams, a microbial ecologist at the University of Florida A & M who was not involved in the study, pointed out that some protists could accidentally ingest the virus. (Even humans Unknowingly swallow a mass of virus every day). “Protists may be very grazing in most cases,” he said. Anything in the protist path within a certain size can go down like many debris and has little nutritional impact.

Even if the virus appears in the protist menu, it’s not clear if it’s a main course or a small side dish. Some protists were sometimes able to snack on the virus as part of their diverse diet, while others feasted on them exclusively. Due to its very small size, Dr. Stepanauscus said that picozoa (less than 3 micrometers wide, or about one-thirtieth the width of human hair) can eat only the virus. “They may not even be able to consume larger particles,” he said.

Curtis Satoru, a microbial ecologist who led some early studies on protists that can eat the virus, said his team’s unpublished experiments could be that certain Choanozoa are also deadly. Said that it suggested

Therefore, the viruses may be terribly criticized, but Dr. Satoru said, “they are great sources of nutrition.”