Virus, discovered the first organism that feeds exclusively on it

Virus, discovered the first organism that feeds exclusively on it


It's called Halteria and it's the first organism we know that can feed exclusively on viruses. Researchers from the University of Nebraska-Lincoln have recounted it in a study just published in PNAS, according to which this creature, a kind of planktonic ciliate that inhabits fresh waters, has managed not only to grow, but its population size by following a virus-only diet.

A rather bizarre fact. We recall, in fact, that viruses are generally consumed incidentally by a vast range of organisms, and in some cases they can also form part of the diet of some marine protists, given that they are provided, for example, with amino acids, lipids, nitrogen and phosphorus. However, to qualify as a step in the food chain, viruses would need to provide a significant amount of energy or nutrients to those who consume them. In the study, in particular, Chlorovirus was used, a giant double-stranded DNA virus known to infect microscopic green algae, make them explode and release carbon and other nutrients into the environment.

Carrying out the analyzes On freshwater samples, the researchers first added chloroviruses to try and see if any organisms were feeding on them. They later observed, using a green dye to mark the virus' DNA, that there were mainly two organisms that fed on the Chlorovirus, Halteria and Paramecium (another ciliate). But with one difference: while Paramecium only made "snacks", and therefore the size and number of organisms remained almost stable, Halteria used Chloroviruses as a source of nutrients. In fact, the analyzes showed that the population of the ciliate had grown by about 15 times in two days, while that of the virus decreased by 100 times.

Although further investigations are needed to confirm these findings in nature, as the researchers point out, the knock-on effects of widespread chlorovirus consumption could have a major impact on the carbon cycle. “If you calculate a rough estimate of how many viruses there are, how many ciliates there are and how much water there is, you get this huge amount of energy moving up the food chain,” says ecologist John DeLong, lead author of the research. . "If this is happening on the scale we estimate, it should completely change our view of the global carbon cycle."