Humans and animals are not the only ones affected by viruses. Unicellular organisms can also be attacked. In a new study, scientists establish that green algae can carry latent giant virus DNA in their genome.
Biology researchers at Lund University in Sweden have spent several years studying microorganisms isolated from Lake Krageholm in Skåne and Lake Örsjön in Småland. During the most recent electron microscopy analyses, the researchers discovered by chance that the common green alga Chlamydomonas was carrying virus-like particles inside the cell.
Across the Atlantic, a research team at Virginia Tech made a similar discovery.
It turned out that their green algal culture contained long viral DNA sequences in its genome, and that the giant virus is latent there. This viral DNA, together with the green algal cell machinery, can form new virus particles. The discovery was the start of a transatlantic research collaboration, the latest results of which have now been published in the scientific journal Science.
"Usually, virus particles cause the whole algal culture to collapse and die, but in this case, the algal cultures are seemingly healthy even though they are producing virus particles in some cells. Previously, it has not been possible to show that this is happening," says Karin Rengefors, professor of biology at Lund University.
Scientists have previously found viral elements in many different organisms. However, it has been unclear whether they were randomly introduced into their host's genome. It has also been unclear whether the viral genome was actually intact and able to produce new virus particles. The Swedish-American research team has now established for the first time that the giant virus has a strategy for spreading, hiding, lying dormant and then producing new viruses.
"The fact that this giant virus Punuivirus, which is present in a large proportion of the green algae we isolated from Swedish lakes, has been integrated into its host's genome may be a strategy for surviving periods of prolonged host dormancy," says Karin Rengefors.
With this new study, Karin Rengefors and her Lund University colleagues Petronella Wessman and Maria Coelho-Svensson hope to contribute to a better understanding of how viruses can spread, stay in a population - without killing it - and build their own genome into that of their host. They also want to strike a blow for independent basic research, and how it can lead to further unexpected discoveries across borders.
"Thanks to Lund University's gender equality programme for visiting professors of underrepresented gender, we came into contact with the world's leading viral expert on algae, Corina Brussard. She helped with the design, analysis and interpretations of our data. Her contribution was crucial," says Karin Rengefors.
In addition to Lund University, the following higher education institutions participated in the project: Virginia Tech, Max Planck Institute for Biology Tübingen, Royal Netherlands Institute for Sea Research, University of Amsterdam, University of Miami.
Publication:
Link to the article in Science:
Cryptic infection of a giant virus in a unicellular green alga
