GBB seminar serie PhD edition Anna Schöntag

Anna Schöntag

Molecular Microbiology

Infection strategies of the archaeal viruses HCTV-6 and HCTV-8 in Haloarcula marismortui

Archaea, like bacteria and eukaryotes, are susceptible to viral infection. The interactions between archaea and their viruses remain highly elusive, and few have been characterized in detail. Haloarchaea and their viruses are used as models to investigate virus-host interactions since they are infected by a range of different viruses and are excellent for microscopy. The haloarchaeon Haloarcula marismortui (formerly Haloarcula californiae ATCC 33799) can be infected by Haloarcula californiae tailed virus 6 (HCTV-6) and Haloarcula californiae tailed virus 8 (HCTV-8) whose representative species belong to the family Hafunaviridae. The interactions between these viruses and their host were characterized and compared using one-step growth experiments and microscopy. HCTV-6 exhibited a clearly lytic infection cycle, while HCTV-8 employed a non-lytic infection strategy. Notwithstanding these differences, infection by either virus resulted in substantial morphological changes in Haloarcula marismortui cells. HCTV-8 prevented secondary infection by homologous virus particles, indicating the presence of a superinfection exclusion mechanism. To investigate the molecular basis of virion release, viral genomes were screened for candidate lysis-associated proteins, and selected genes were heterologously expressed in Haloferax volcanii. This approach identified a small viral protein capable of inducing cell lysis, suggesting a role in virion egress. Collectively, the characterization of these two previously unstudied haloarchaeal viruses provides new insights into the diversity of virus-host interactions and virion release mechanisms in haloarchaea.