A University of Nebraska-Lincoln research team recently published an article in Proceedings of the National Academy of Sciences that details Halteria eating chlorovirus when deprived of other food sources:
To test the hypothesis, DeLong and his team collected samples of pond water, isolated different microbes, and then added large amounts of chlorovirus, a freshwater inhabitant that infects green algae. Over the next few days the team tracked the population size of the viruses and the other microbes to see if the latter was eating the former.
And sure enough, one particular microbe seemed to be snacking on the viruses – a ciliate known as Halteria. In water samples with no other food source for the ciliates, Halteria populations grew by about 15 times within two days, while chlorovirus levels dropped 100-fold. In control samples without the virus, Halteria didn't grow at all.