How Viruses Enter Microorganisms

The biologist Dr. Tessa Quax from the University of Freiburg has acquired 1.7 million euros in funding from the Deutsche Forschungsgemeinschaft (German Research Foundation, DFG) for an Emmy Noether junior research group. Under her leadership, for the next five years the group will research how viruses are able to infect archaea – single cell microorganisms without a nucleus. The project will begin June 1, 2019.

Archaea are one of the three domains of life; the other two are bacteria and eukaryotes, which are organisms that have a nucleus and organelles. Archaea can be found in many different habitats, from the deep sea to the human digestive system. Like most living cells, archaea can be infected by viruses. However, the molecular mechanisms on which this infection is based have not been researched to date.

Compared to bacterial and eukaryotic viruses, the variety of external shapes and genetic makeup of the archaeal viruses that have been studied so far is especially large. Bacterial viruses use thread-like structures on the surface of host cells to attach themselves and infect them. For example, they rely on the flagella that bacteria use to move around, or on tiny appendages called pili with which bacteria attach themselves to surfaces. There are indications that archaeal viruses also use such thread-like structures on the cellular surface of archaea to infect them. Some of these archaeal structures, like pili, are similar to those on bacteria. On the other hand, the composition and structural organization of the archaeon’s propulsion organ, the archaellum, is fundamentally different from the bacterial flagellum.

Tessa Quax and her research group want to discover whether archaeal viruses use the surface structures of archaea to infect them, and if so, how this occurs. The researchers are using Haloferax volcanii, an archaeon that can be genetically manipulated, as a model system for their study. The goal of their project is to precisely determine the composition of archaeal surface structures and to study how virus infections can occur. They also want to investigate archaeal viruses and better understand their infection strategies.

“The goal of the project is to expand our knowledge of archaeal viruses, of which relatively little has been researched to date – especially their interaction with cellular surface structures,” says Quax. “This information could help us to better understand viral diversity and evolution. Our project also focuses on basic aspects of the cell biology of archaea as well as how they interact with the environment, which is important for the colonization of new habitats.”