‘Viróvore’: organism discovered that feeds on viruses

In December 2022, microbiologist John DeLong, from the University of Nebraska-Lincoln, in the United States, published his final study in PNAS on a microbe that feeds only on viruses.

From the class of viróvora, the hitherto unknown organism is a unicellular ciliate that lives in fresh water and can feed only on viruses and thrive. Since viruses are made of nucleic acids, lots of nitrogen and phosphorus, DeLong notes that it makes sense that nature learned to eat them, as they are really good raw materials.

The nutritional bonus

(Source: IFLScience/Reproduction)

DeLong and his team arrived at this conclusion by adding chlorovirus to the water of a small pond full of microbes. They observed that the population number of a microbe of the genus Halteria in particular has increased over time, while the amount of chlorovirus in the water has plummeted.

To make sure the organism was indeed consuming the viruses, its DNA was filled with a fluorescent dye, which appeared on the microbe as confirmation. O Halteria not only does it gobble up the virus, it grows stronger and healthier as it does so.

Each Halteria managed to ingest between 10,000 and 1 million chloroviruses in one day. After more than 48 hours of exposure, the viral load plummeted 100-fold in the lagoon, with the protist population growing an average of 15-fold over the same period.

(Source: WION/Reproduction)(Source: WION/Reproduction)

Ecologist Joshua Weitz, leader of a research group at the Georgia Institute of Technology on the role of viral entities in the life cycle, argues that viruses are potentially nutritious if swallowed by a microbe that digests them and is not infected by them.

The healthy growth of microbes is explained because, in general, viruses are composed of genetic material (DNA or RNA) and viral genomes are densely packed. And because the genetic material is rich in phosphorus, viruses have a higher content of this element than typical microbes, becoming a nutritional bonus.

What changes

(Source: Mashable India/Reproduction)(Source: Mashable India/Reproduction)

This phenomenon already changes everything, forcing biologists to reexamine everything that is known about the life cycle so far and what is its role in the environment, since, when infecting all types of living beings, viruses burst, releasing matter organic matter and nutrients in the atmosphere, which can affect carbon levels and the role it plays in food chains.

When chloroviruses infect algae, causing them to explode and release the carbon contained in them back into the water, it prevents herbivores from absorbing energy up the food chain by keeping the carbon low in a kind of layer of microbial soup.

When the virus was consumed by the Halteria, the carbon stored within it was worked back up the food chain as larger organisms consumed the ciliate, helping to balance carbon levels in the food chain through a type of natural carbon recycling. That is, it results in an immeasurable amount of energy movement.

(Source: NOAA/Reproduction)(Source: NOAA/Reproduction)

At the moment, more research is underway to confirm that the same virus ingestion behavior happens in nature just like in a controlled environment such as the laboratory.

Still, as Weitz points out, this research is already an important step forward in advancing science in understanding the ways in which viral particles are involved in moving energy (and nutrients) both up and down microbial food webs—even though quantifying the role of the virus as a transmitter of energy and nutrients is not an easy task.