About This Project

The discovery of giant viruses, that are larger than bacteria and encode translational and metabolic machinery, is challenging the definition of a virus and what constitutes a living organism. Because giant viruses are so different, they have likely been overlooked in previous studies, hence their role in ocean ecosystems can only now begin to be understood. This project will find new giant viruses and characterise them, to inform studies examining their impact on ocean microbial communities.

Ask the Scientists

What is the context of this research?

The first giant virus discovered was so large it was mistaken for a bacterium, and was called Mimivirus as it "mimicked" bacteria. Later, Tupanvirus was found to encode many genes involved in translation, which normally are provided by the host cell. Giant viruses hence redefine what a virus is, and what differentiates them from cellular life.

Because of these differences, giant viruses will have been missed in studies isolating new viruses, as they are removed by filtration and other routine methods.

Giant viruses are likely key players in oceans, however. Viruses control microbial growth. Giant viruses infect protists, many of which in turn feed on bacteria. They also encode metabolic genes. They could hence significantly influence marine food chains and biogeochemical cycles.

What is the significance of this project?

Because there are relatively few examples of giant viruses that have been isolated and characterised in vitro, establishing a mechanistic understanding of how they infect and replicate, and how this activity relates to their genes and proteins, remains a current challenge.

This project will isolate new giant viruses from water samples taken from the ocean. The genome, structural proteins, and host range of isolated viruses will be characterised. With this insight, the giant virus lifecycle can be described in more detail.

This understanding will inform our understanding of how giant viruses influence their marine hosts, and in turn nutrient cycles. We can then begin to ask how factors like ocean warming impact marine virus-host interactions.

What are the goals of the project?

This study aims to isolate and characterise novel giant viruses from the ocean. To isolate viruses, water samples will undergo enrichment in growth media, filtration and centrifugation. Genomic DNA will be extracted using standard viral DNA extraction kits and sequenced by Illumina. The size and content of the genome, and how this controls infection and assembly, will be assessed. The structural components of virions will be analysed using SDS-PAGE and electron microscopy, helping to explain the structural basis of assembly and infection. Genes and proteins will be assigned function using sequence alignment/BLAST and structure prediction, identifying which proteins are involved in which stage of the virus lifecycle.