Saturday, January 28, 2023

First confirmed virus: The little jumper Halteria virus lives and grows on food

A carnivore is an organism that obtains its energy and nutritional requirements primarily or exclusively through a diet consisting of meat consumption. A herbivore, same thing but with plants… So, what is a herbivore? Well, an organism that obtains energy and nutrients by consuming viruses.

If you search for this word in the RAE dictionary, you will not get any answer. The first definition on Wikipedia is from last December 28 (in the English version, virus,

The first study indicating the possibility that some species of unicellular protists are capable of consuming viruses was in the 1980s. In recent years, results of several other investigations related to the flow of viruses in ponds and sewage water have come to the fore. In September 2020, an article published in the journal Frontiers in Microbiology reported the first ever case of a protista ingesting a virus in seawater.

first detailed study

A team led by John DeLong from the University of Nebraska-Lincoln (USA) has now published (in the journal December 27, 2022). PNAS) Results of a study that show in detail for the first time the activity of protists (of the genus Halteria) capable of consuming enough virus particles to ensure their survival and growth.

The study also indicates, as a novelty, that the virus-based feeding of protists is an important part of food networks or chains in ecosystems such as ponds, lakes, rivers and even in the ocean. Until now, the new study indicates, ecologists didn’t take into account this basic trophic link: viruses are consumed by protists, protists are consumed by zooplankton, zooplankton are consumed by fish…” Consumption returns energy to food chains”, is the title of the now published Scientific American article.

short and bouncy

Heltaria is a genus of freshwater clade, between 15 and 35 µm (μm) long, of which about twenty species are known. They have a spherical shape and at one pole they have a crown of cilia that are located in the vicinity of the oral region and serve directly for feeding. In addition, they have other long cilia which are arranged in an equatorial shape and which are used as oars for jumping: for this reason they are also known as jumping ciliates.

The University of Nebraska-Lincoln has published an informative article on the research led by John DeLong, noting that “for the first time, this team’s laboratory experiments have shown that protein has been shown to promote physical development and even growth.” For virus-only diet is enough.” An increase in the population of an organism.

The authors performed experiments with water containing chloroviruses and algae, and compared the response in the presence of Halteria sp., why Paramecium bursaria. “nOur feeding trials demonstrated robust growth in Halteria populations with only chlorovirus as food,” in the article PNAS.

Illustration of scientific article indicating the formation of plaques in the presence of Halteria and Paramedium in water containing chlorovirus.


DeLong’s team specifically took samples from a pond near their lab and mixed different microorganisms into droplet-sized samples.

“After 24 hours, DeLong looked in the droppings for a sign that some species were enjoying the company of chloroviruses, even as one species viewed the virus as a snack and less of a threat.” was,” says the disclosure note Chlorovirus College.

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The result was that the chlorovirus dropped by 100-fold in just two days, while the Halteria population, with nothing to eat, was growing an average of 15-fold over the same time period.

To confirm that the helateria were indeed consuming the virus, the team tagged some of the chlorovirus DNA with a green fluorescent dye before introducing the virus to the ciliates. Sure enough, the ciliated equivalent of the stomach, its vacuole, soon glowed green.

“It was unmistakable: The ciliates were eating a virus. And that virus was sustaining them,” says DeLong.

“If you roughly estimate how many viruses there are, how many ciliates there are, and how much water there is, you get this enormous amount of energy moving (the food chain),” said DeLong, who estimated that ciliates are a In a small pond, they can eat 10 trillion viruses in a day. “If this is happening on the scale that we think it could, it should completely change our view of the global carbon cycle,” says the study’s lead author.

Protista: a mixed bag kingdom

The RAE dictionary defines the word Protista as: Biol. Said of a living organism: composed of a single eukaryotic cell or of several that are not associated to form tissue; P. For example, Protozoa.
The biological classification of the five kingdoms of living beings (most commonly recognized by experts today) indicates that the Protista kingdom includes eukaryotic organisms (that is, those whose cells contain a cell nucleus), which are neither animals nor plants. . No mushroom. In other words, a mixed bag for microbes that are difficult to classify.
Most species of protists are unicellular, and do not have relatively simple multicellular or multicellular structures.

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