Infection mechanisms of archaeal viruses
We are interested in the infection mechanisms of archaeal viruses. We focus specifically on viruses of halophilic archaea as they offer the exciting possibility to combine genetics with life cell imaging and fluorescent microscopy approaches, allowing the study of dynamics of infection. In nature, halophilic microorganisms are outnumbered 10-100 fold by viruses and consequently in a constant interplay with them. Archaeal viruses are famous for the high diversity of their virion morphologies, but relatively little is known about their infection strategies. We study the infection mechanisms that archaeal viruses employ in order to enter the host cell, establish an successful infection and to redirect the cellular recourses for their own reproduction. The bacterial and archaeal cell envelopes are fundamentally different, and consequently archaeal viruses face different challenges as their bacterial counterparts. For only a handful of these archaeal viruses, entry and egress strategies have been studied. In a few cases, strategies are employed that resemble those of bacterial viruses, while others are unique for archaeal viruses, such as the egress mechanism of some crenarchaeal viruses that relies on the formation of pyramidal shaped structures on the host cell surface. We aim to characterize more infection strategies of archaeal viruses, in order to shed light onto the viral evolutionary history and adaptation to extreme environments.
Bacteria and archaea can perform tactic behavior and thereby move up and down chemical gradients. This tactic behavior relies on a motility structure, which can be guided by a chemosensory system. Motility along chemical gradients, chemotaxis, relies on the response regulator CheY. When phosphorylated, bacterial CheY inverses the rotational direction of the flagellum via a switch complex at the base of the motor. Interestingly, some archaea, like euryarchaea, also possess the chemotaxis system. Bacteria and archaea have developed fundamentally different rotary motors enabling their motility, termed flagellum and archaellum respectively. The structural difference between these motors raises the question how the chemotaxis system can communicate with the archaeal specific motility machinery. Therefore, we aim to identify and structurally characterize the archaeal switch complex at the base of the archaellum motor. We apply genetic and fluorescent microscopy techniques to study the role and organization of chemotaxis and archaellum proteins in the halophile Haloferax volcanii. The functional analysis of these proteins might provide mechanistic insights in how archaea transfer environmental signals to the motility machinery. This information is especially relevant to understand how archaea perform directional movement and colonize new habitats.