Giant viruses in the wild

In an new project, researchers at the University of Viennas Centre for Microbiology and Environmental Systems Science (CeMESS) investigate the diversity and ecology of giant viruses and their microbial hosts. Understanding viruses and virus-microbe interactions are fundamental aspects of biology, with implications reaching far beyond the microscopic world. These interactions not only shape the dynamics of microbial communities but also influence larger ecological processes, such as nutrient cycling, and even the health of macroscopic organisms, including humans. An unusual group of viruses discovered only recently are the giant viruses. These viruses infect single-cell eukaryotes, also called protists, and challenge our understanding of the viral microbial world. Viruses are known for their tiny size and simplicity, but giant viruses break this mold by being as large as bacteria, both in physical size and genetic complexity. These unique characteristics raise questions about how they evolved, and how they interact with their protist hosts and impact ecosystems. Protists are vital components of the microbial world and play a crucial role in microbial food webs. These microscopic eukaryotic organisms act as linchpins in various ecosystems, linking primary producers to higher trophic levels. By grazing on bacteria and algae, protists regulate the abundance of these microorganisms, thereby influencing nutrient cycling and energy flow within ecosystems. Furthermore, protists themselves serve as both consumers and prey, making their interactions with viruses integral to understanding the intricate web of life within aquatic and terrestrial environments. In the present project, the research team around Matthias Horn at CeMESS sets out to explore the diversity of giant viruses infecting protists in selected environments and aims to better understand how they impact microbial communities. To achieve this, the scientists will employ innovative methods to discover and study new giant viruses. They will collect samples from different environments and aim to isolate giant viruses using protists as hosts that have rarely been used for this purpose before. Experiments will be conducted to understand how these giant viruses interact with their protist hosts and other microorganisms in complex communities. Additionally, the research team analyzes their genetic makeup to elucidate the evolutionary history of this unique group of viruses. The project team has previously been involved in the discovery and characterization of the giant viruses Viennavirus and Klosneuvirus, both showing unique properties and originating from a waste water treatment plant near Vienna. The current project will help to further explore the enigmatic world of giant viruses, offering us the opportunity to discover new insights about their interactions with their protist hosts and the consequences for complex microbial communities.