Scientists first discovered an organism that feeds only on viruses

Since viruses are found absolutely everywhere, it is inevitable that some organisms will consume them by accident. But researcher John DeLong of the University of Nebraska at Lincoln, USA, wanted to find out if any microbes could be eating viruses on purpose. And such organisms were found - tiny ciliates, distant relatives of the well-known ciliates-shoes.

In his research DeLonge and his team collected pond water samples, isolated various microbes, and then added large amounts of chlorovirus, a freshwater resident that infects green algae. Over the next few days, the team tracked the population size of viruses and other microbes to reveal the food chain.

And indeed, one particular microbe seems to have been snacking on viruses - a ciliate known as Halteria. In water samples where there was no other food source for the ciliates, Halteria populations rose about 15-fold within two days, and chlorovirus levels dropped 100-fold. In control samples without virus, halteria did not grow at all.

In subsequent tests, the team tagged the DNA of the chlorovirus with a fluorescent dye and found that the halteria cells soon began to glow. This helped confirm that they had indeed consumed the virus.

These experiments show that the newly coined term "virovory" can now take its place among herbivores, carnivores, and omnivores. But, of course, Halteria is unlikely to become the only representative of this group. The researchers plan to continue studying them, identifying the impact on food webs and larger systems.