These microbes are the first known to only be able to eat viruses

New year, new viral diet — literally.

Tiny, living in a pond Dumbbells ciliates are vivororesable to survive on a viral-only diet, researchers report Dec. 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 certain microscopic organisms nibble on aquatic viruses like chloroviruses, which infect and kill algae. But it was unclear whether viruses alone could provide enough nutrients for an organism to grow and reproduce, says ecologist John DeLong of the University of Nebraska-Lincoln.

In laboratory experiments, Dumbbells that lived in water droplets and received only chloroviruses for sustenance reproduced, DeLong and his colleagues found. As the number of viruses in the water decreased, Dumbbells the numbers have increased. Ciliates without access to viral bits, or any other food, did not multiply. But Parameciumlarger microbe, did not thrive on a virus-only diet, suggesting that viruses cannot meet the nutritional requirements for all ciliates to thrive.

Viruses could be a good source of phosphorus, which is essential for making copies of genetic material, DeLong says. But it probably takes a lot of virus to explain a full meal.

In the laboratory, each Dumbbells microbe ate about 10,000 to 1 million viruses a day, the team estimates. Dumbbells in small ponds with abundant viral snacks, they could ingest about a quadrillion virus per day.

These feasts could divert previously unrecognized energy into the food web and add a new layer to how viruses move carbon through an ecosystem – if it happens in nature, says DeLong (SN: 09/06/16). His team plans to start finding out once Nebraska’s ponds thaw.