Tiny ciliates Halteria living in ponds, are divers able to survive on a diet containing only viruses, researchers reported on December 27 Proceedings of the National Academy of Sciences . Single-celled creatures are the first known to thrive when only viruses are on the menu.
Scientists already knew that some microscopic organisms feasted on aquatic viruses, such as chloroviruses, which infect and kill algae. But it was unclear whether the viruses themselves could provide the body with enough nutrients to grow and reproduce, says ecologist John DeLong of the University of Nebraska-Lincoln.
DeLong and his colleagues found that in laboratory experiments Halteria , which lived in water droplets and received only chloroviruses for existence, reproduced. As the number of viruses in the water decreased, the amount Halteria grew up Infusoria without access to viral particles or any other food did not reproduce. But Paramecium a larger microbe, did not thrive on a virus-only diet, suggesting that viruses cannot meet the nutritional requirements for the growth of all ciliates.
Viruses can be a good source of the phosphorus needed to make copies of genetic material, DeLong says. But apparently it takes a lot of viruses to eat a full meal.
Every microbe in the laboratory Halteria ate about 10,000 to 1 million viruses each day, the team estimated. Haltering in small ponds with lots of virus snacks can kill about a quadrillion viruses per day.
These feasts can shunt previously unknown energy into the food web and add a new layer to how viruses move carbon through the ecosystem—if it occurs in the wild, DeLong says. His team plans to begin research as soon as the reservoirs in Nebraska thaw.
