Creatures feeding on viruses

A surprising discovery. Scientists discover, for the first time, creatures feeding on viruses.

virus as food

Viruses are found in astronomical numbers all over Earth, from the atmosphere to the depths of the oceans. Even its biomass is equivalent to about 25 billion people, but the strange thing, despite its abundance and richness in nutrients, is that there are no known living organisms that use it for food.

There is a growing body of evidence indicating that at least one group of organisms can feed on viruses, namely "protozoa and unicellular microorganisms".

Researchers in Frontiers in Microbiology published on September 24, 2020, the first convincing evidence that two groups of environmentally important marine primate organisms, namely Choanozoa and picozoa, two virus eaters, hunt their prey in a process. Ingestion.

A big surprise.

Dr. Ramunas Stepanauskas is the study leader and director of the Center for Single Cell Genomics at the Bigelow Laboratory for Ocean Sciences in Maine.

"Our data shows that many precursor cells contain the DNA genes of a wide variety of non-infectious viruses rather than bacteria, which clearly shows that they feed on viruses rather than bacteria. This was a big surprise," says Stepanauskas.

He adds that these results contradict prevailing views on the role of viruses and protozoa in marine food webs.

If the results of the study are correct, then a centuries-old doctrine will be turned upside down, instead of seeing viruses only as pathogens and seeing them play a role in nourishing and sustaining life.

"Viruses are rich in phosphorous and nitrogen, and they can be a good supplement to a diet rich in carbon," says Julia Brown, a microbiologist at Bigelow Laboratory and first author of the study, in the press release published on the science website Eurek Alert. . Also, "removing viruses from the water may reduce the number of viruses available to infect other organisms."

Sample collection and analysis.

Ramunas Stepanuskas and his colleagues started this research project more than ten years ago. Initially, they intended to study the pioneer marine preferences for prey, many of which feed on bacteria, but the results surprised them.

Surface seawater samples, including 1,698 pioneer individuals, were collected from the northwest Atlantic Ocean in the Gulf of Maine, the United States in 2009, and from the Mediterranean Sea off Catalonia, Spain, in 2016.

Stepanuskas and his colleagues then divided the cells and analyzed their contents. The team concluded that any genetic material that differs from the genetic material of protists may be a sign of something they ate.

After several rounds of analyzes, the researchers were surprised to find that there was not much bacterial material to be found. Instead, there were viruses of all shapes and sizes. Even viral genes were found in the cells of all the precursors of the funiculus and picosa groups.

It was a strange discovery, says Julia Brown. Although, since the 1990s, researchers have speculated that some early species could use viruses for food, this research did not receive much attention thereafter.

The issue of viral consumption.

However, finding viral genetic material in or around a cell does not guarantee that the virus was once food. For example, some viruses may have infected protists or just be stuck to the surface of cells.

However, Dr. Brown says it is "very unlikely that these viruses will be able to infect all the protists in which they are found."

"The new study alone cannot demonstrate the consuming relationship between protists and viruses," says Rika Anderson, a microbial ecologist at Carleton College in Minnesota who was not involved in the study, in a published report. in the New York Times.

But protists are found in a bewildering array of habitats, such as rotting tree stumps and animal guts, and they may have at least developed several strategies for foraging. “They eat everything, I wouldn't be surprised if they fed on viruses. "

Dr. Stepanauskas and Dr. Brown say that certain types of viruses are only found in certain groups of protists, suggesting that this was not just a coincidence.