Supplementary Material for: Reclassification of Giant Viruses Composing a Fourth Domain of Life in the New Order Megavirales

Interest in giant viruses has risen sharply since 2003, following the discovery of the Mimivirus and four other protist-infecting giant viruses that are linked to the nucleocytoplasmic large DNA viruses (NCLDVs). Despite considerable heterogeneity in hosts and genome sizes, the NCLDVs have been shown to be monophyletic based on analyses of their sequences and gene repertoires and recent studies have proposed that these viruses share a common ancient ancestor and compose a fourth domain of life. In addition, several characteristics of these giant viruses contradict or do not match the criteria used for the canonical definition of viruses, and the NCLDV denomination is not completely appropriate. We propose here to define a new viral order named Megavirales.

自2003年发现拟菌病毒（Mimivirus）以及另外四种寄生于原生生物、隶属于核质大DNA病毒（nucleocytoplasmic large DNA viruses, NCLDVs）的巨型病毒以来，学界对巨型病毒的研究兴趣急剧攀升。尽管这类病毒在宿主范围与基因组大小上存在显著异质性，但基于序列与基因组成的分析已证实核质大DNA病毒（NCLDVs）为单系类群；近期研究进一步提出，这类病毒拥有共同的古老祖先，可构成生命的第四个域。此外，这类巨型病毒的多项特征与经典病毒定义的标准相悖或并不契合，“核质大DNA病毒（NCLDVs）”这一命名也并非完全恰当。我们在此提议设立一个新的病毒目，命名为巨病毒目（Megavirales）。