Giant viruses as symbionts in amoeba

The discovery of giant viruses changed our perception of the viral world. With genome and particle sizes comparable to those of bacteria and a number of cellular features, such as nearly complete sets of translation-related genes, giant viruses sparked a heated debate about the evolutionary origin of these unusual viruses of protists and other unicellular microbes. Host-switches and competition with intracellular bacterial symbionts were proposed as important drivers of giant virus evolution. Yet, bacteria-virus interactions in protists are poorly understood. Furthermore, only very few hosts were used for the isolation of giant viruses.

Aim: To isolate new giant viruses their amoebae host as well symbiotic bacteria associated with the host. In addition to well-mastered model systems, also exotic hosts will be used for giant virus isolation. Subsequently, the replication cycles and the genomic features of the isolated giant viruses will be studied. Furthermore, interactions of giant viruses and their hosts, as well as symbiotic bacteria, will be investigated.

Approach: Giant viruses, amoebae and amoeba symbionts will be isolated from different environments. Subsequently, the replication/life cycles and interactions of the isolated organisms will be studied with Fluorescence in situ hybridization (FISH), Electron microscopy (EM) and quantitative PCR. Additionally, the genomes of giant viruses will be sequenced and phylogenetic analysis and genome comparisons will be performed.

Relevance: This project will improve our knowledge on the diversity of giant viruses and their hosts. Furthermore, it will help to understand the enigmatic evolution of giant viruses by investigating different interactions of giant viruses with their host as well as symbiotic bacteria of the host.

Student: Patrick Arthofer

Faculty: Horn (PI)

Funding: Universität Wien

Selected publications:

Boyer, M., Yutin, N., Pagnier, I., Barrassi, L., Fournous, G., Espinosa, L., … Raoult, D. (2009). Giant Marseillevirus highlights the role of amoebae as a melting pot in emergence of chimeric microorganisms. Proceedings of the National Academy of Sciences, 106(51), 21848–21853. https://doi.org/10.1073/pnas.0911354106

Filée, J. (2015). Genomic comparison of closely related Giant Viruses supports an accordion-like model of evolution. Frontiers in Microbiology, 6(MAY), 1–13. https://doi.org/10.3389/fmicb.2015.00593

Boyer et al., (2011) Mimivirus shows dramatic genome reduction after intraamoebal culture. Proceedings of the National Academy of Sciences, 108(41), 17234–17234. https://doi.org/10.1073/pnas.1114908108

Li, Y., Hingamp, P., Watai, H., Endo, H., Yoshida, T., & Ogata, H. (2018). Degenerate PCR primers to reveal the diversity of giant viruses in coastal waters. Viruses, 10(9), 1–16. https://doi.org/10.3390/v10090496

Mueller, L., Bertelli, C., Pillonel, T., Salamin, N., & Greub, G. (2017). One year genome evolution of lausannevirus in allopatric versus sympatric conditions. Genome Biology and Evolution, 9(6), 1432–1449. https://doi.org/10.1093/gbe/evx074