Grapevine

Hunting down giant viruses that attack tiny algae

They were said to come from outer space, and there were even claims that they were actually bacteria and that they undermined the very definition of viruses. Giant viruses, nicknamed "giruses," contain enormous quantities of genetic material—up to 100 times more than other viruses—and some are larger than certain bacteria.

They were practically unknown to science until the early 21st century, yet discoveries made over the past two decades suggest that they can have a major impact on life on Earth.

Giant viruses inhabiting the oceans infect, among others, various species of single-celled algae, photosynthetic organisms that are responsible for about half of the Earth's oxygen production and around half of the global carbon fixation.

Viral infection can cause a rapid collapse of algal blooms—accumulations of algae stretching across tens of thousands of kilometers in the ocean—and this can, in turn, substantially affect extensive marine, atmospheric and terrestrial ecosystems. However, we still know very little about the natural hosts of giant viruses, that is, which species of algae are infected by each type of virus.

In a study, published in Nature Microbiology, researchers from Prof. Assaf Vardi's lab in the Plant and Environmental Sciences Department at the Weizmann Institute of Science used single-cell RNA sequencing to analyze samples collected from an algal bloom in the fjords of Norway.