Scientists say they have found a virus in the coastal waters off Oahu, Hawaii that has some unusual characteristics.

The team from Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE) at the University of Hawai'i (UH) at M?noa described the finding in the journal Virology.

Named TetV-1, it infects single-celled algae called Tetraselmis. It’s so big that it rivals bacteria in size, putting it in the character of “giant viruses”. More and more of these larger variants have been found in the last 15 years, increasing their known sizes.

“Most viruses are so tiny that we need an electron microscope to see them,” Grieg Steward, professor in the UH M?noa Department of Oceanography and co-author on the study, said in a statement. “[B]ut these giants rival bacteria in size, and their genomes often code for functions we have never seen in viruses before.”

In the study, the team sequenced the genome of the virus and found that it had a number of genes picked up from Tetraselmis. This included two genes related to the process of fermentation, which is how microorganisms get energy from sugars.

It’s not quite clear why the virus has these genes, but it may be that the algae turns the water from clear blue to green. The fermentation genes may therefore allow TetV to thrive in these low oxygen conditions, with it finding a home inside algae.

“The TetV genome is the largest sequenced to date for a virus that infects a photosynthetic organism, and its genes reveal unprecedented mechanisms by which viruses manipulate their host's metabolism,” the team wrote in their paper.

Researching viruses like this is important, as they can have a dramatic effect on the food source of animals. They can spread through populations of phytoplankton, causing their cells to disintegrate and decompose. Tetraselmis itself is a food source, and also a source of starch for the biofuel industry.

“That sounds bad,” said Steward, “but viruses actually help maintain balance in the marine ecosystem. Viruses spread more efficiently through highly concentrated populations, so if one type of phytoplankton grows faster than the others and starts to dominate, it can get knocked down to lower levels by a viral infection, giving the other species a chance to thrive.”

The team now plan to carry out field and laboratory experiments to see if their theory about the virus genes is correct. But, they note, it is likely just one of millions of other viruses that are awaiting discovery.