GIVIREVOL · Host range and genome adaptation of giant viruses

For more than a century, viruses were considered tiny particles, fully dependent on their host cells to replicate. The recent discovery of giant viruses, containing unusually large genomes, challenged this assumption and blurred the sharp division between viruses and cellular life. It was also striking to learn that many of the giant virus genomes encode translation-related genes, indicating that they are presumably more independent -in terms of translation- as compared to other viruses and potentially infect and replicate in a broad range of hosts. Nonetheless, for most of the giant viruses, the precise host range and natural host species remain to be investigated.In the proposed project, I will investigate the host range and genome adaptation of giant viruses by combining in silico and wet-lab strategies. I postulate that, codon usage is an important factor in the adaptation of giant viruses to their hosts, where well-adapted codon usage provides for superior viral fitness. I will analyse the codon usage preferences among giant viruses and correlate these with the known and presumable hosts they infect. This will allow me to computationally predict the best-suited hosts, and subsequently, experimentally assess my predictions on different laboratory hosts. To further investigate whether codon usage defines the rate of genome adaptation of giant viruses, I will perform experimental evolution over a half year time period.The origin and evolutionary history of giant viruses is controversially discussed. By investigating the evolutionary relationships between giant viruses and their hosts in the context of their codon usage preferences, I will contribute to a better understanding of the factors determining host range and the evolutionary processes shaping giant virus genomes. Disentangling the connection between genomic content and host range will provide important knowledge in the fields of virology, evolutionary biology, genomics, and virus-host interactions.