General, Research, Technology

Organisms eating viruses have been found. What is known about them?

Life on our planet is so amazing anddiverse, that it contains organisms that feed on viruses. Although it would seem - well, who would take it into their heads to eat them? In fact, there is a veritable buffet of viruses on the dinner plate, which is essentially the Earth. It is certainly a bit confusing that scientists have not yet identified a species that deliberately eats viruses for energy, but there is growing evidence that at least one group of organisms can feed on nutrient-rich viruses: protists, microscopic and often single-celled organisms that scientists have struggled to place on the tree of life. Like viruses, protists boil in the billions and trillions of seawater - and some of them, according to a recently published study, may feed on marine viruses. If the results are correct, they could turn a centuries-old dogma upside down: instead of acting only as pathogens of chaos and destroying life, viruses can, in some cases, play a role in nourishing and maintaining it.

Here is an electron micrograph of a colony of choanoflagellate rosettes. Researchers are investigating whether these single-celled organisms can feed on viruses in the world's oceans.

Who feeds on viruses?

So, the authors of a scientific work published inSeptember 2020, the journal Frontiers in Microbiology announced the discovery of two organisms that feed on viruses. This is the first reliable discovery of this type of creature in history.

“The data obtained during the work show thatmany protist cells contain DNA from a wide variety of non-infectious viruses, but not bacteria, which is compelling evidence that they feed on viruses, not bacteria, ”said study co-author Ramunas Stepanauskas, a microbiologist at the Bigelow Oceanology Laboratory in Maine, cites the portal In fact, the importance of the new discovery is difficult to overestimate, since the results obtained contradict the currently prevailing views on the role of viruses and protists in the marine food chain.

The kingdom of protists Is a group of eukaryotic organisms that are distinguished by their diversity. It is noteworthy that most protists are unicellular and less complex in structure than other eukaryotes.

Despite the fact that in itself a scientific workunable to establish a link between protists and viruses, the researchers note that protists have been found in a variety of habitats, from rotting tree stumps to animal guts, and may have developed at least as many behavioral strategies to feed and survive. So these simplest organisms, apparently, feed on everything, they may well afford to feast on viruses.

Interestingly, the research team underthe leadership of Ramunas Stepanauskas started this project more than ten years ago. Scientists originally set out to study the predatory preferences of marine protists, many of which feed on bacteria. But science does not stand still, and now we know that protists eat other single cells.

A fluorescence-activated cell sorter used to separate individual protist cells in Bigelow's Ocean Science Laboratory.

During the study, scientists collected samplesseawater from the Gulf of Maine and the Mediterranean Sea and have isolated nearly 1,700 individual protists. Then they opened the cells one at a time and analyzed their contents. Any genetic material that was different from the protist material, according to the researchers, was likely the signature of something eaten by the microbes. So, in two types of tiny creatures known as choanozoans and picozoans, the researchers found samples of the viral genetic code - and since none of them are vulnerable to viral infection, scientists believe that protists often bite into viruses.

This is interesting: Evolution of disease: the history of fighting viruses

Strange organisms

However, repeated rounds of analysis at the same timesurprised and disappointed scientists. The fact is that in the collected samples, a large amount of bacterial material was not found. Instead, researchers were faced with viruses of all shapes and sizes, sometimes destroying dozens of cells. In the past, protists from two groups, choanozoa and picozoa, have never been found without viral genes in their cellular load, although as early as the 1990s, researchers suggested that some protist species might be able to co-opt viruses into food.

According to The New York Times, in some earlyIn experiments, scientists mixed two types of microbes together in a laboratory to see if protists would consume and digest viruses. But, despite the encouraging results, relatively little attention was paid to this area of ​​research in subsequent years.

The new discovery proves once again that we still do not know much about our home planet and the organisms that inhabit it.

Meanwhile, genetic experiments thatexamining one cell at a time can help strengthen the case for viral consumption by showing that protists ate in vivo is much the same as examining the stomach contents of a predatory wild animal. Technologies that are accurate and powerful enough for such research have only emerged in recent years.

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And yet, detection of viral geneticthe material in or around the cage does not guarantee that the virus was once a meal. For example, some viruses could infect protists or simply adhere to the surface of cells. But there is another interesting possibility. It lies in the fact that viruses infected bacteria, which were then absorbed by protists, creating a kind of microbial roll. But viral and bacterial genetic material isn't always tracked together, so some protists may have missed a middleman and headed straight for the viral meal.

Henry Williams, Florida microbiologistthe university, which was not involved in the study, noted that some protists could inadvertently ingest viruses. "Probably, most of the time, protists are in intensive walking mode, and everything that comes their way and within a certain size range can be destroyed," he said.

But if viruses do appear on the menuprotists, it remains unclear whether they are a main course or a pathetic side dish. Some protists may occasionally snack on viruses that can be part of their varied diet, while others feed exclusively on them. “Viruses are rich in phosphorus and nitrogen and could potentially be a good addition to a carbon-rich diet, which could include cellular prey or carbon-rich marine colloids,” the researchers write in their paper.

One way or another, while other scientists checkthe conclusions of the research of the team of Ramunas Stepanauskas, today it is safe to say - tiny organisms feeding on viruses are a rarity in the Earth's ecosystem.