20 years of research on giant viruses

The discovery of mimivirus in 2003 expanded the boundaries of virology, revealing giant viruses with particle sizes and gene contents comparable to those of cellular microbes. Sampling expeditions have since shown that mimivirus relatives are widespread in environments where they infect unicellular eukaryotes, playing active roles in various ecosystems.
This presentation will explore the infectious cycle of mimivirus and key features of its virion. Similar sampling strategies led to the isolation of other viral families, including Marseilleviridae, whose study brought unexpected insights. Just as the limits of viral complexity seemed within reach, the discovery of Pandoraviridae challenged assumptions with over 1-micron-long particles and genomes up to 2.8 Mb, encoding mostly unique proteins.
Further exploration of >30,000-year-old permafrost samples resulted in the reactivation of ancient pithovirus and mollivirus sibericum in modern amoebae. The Pithoviridae family has since grown, with both ancient and modern members now classified into three clades. In contrast, only two modern mollivirus isolates have been identified so far.
To conclude, I will briefly discuss recent findings on mimivirus infection cycle, shedding light on the origin and evolution of DNA viruses and their potential link to the emergence of eukaryotes.