Abstract
Giant viruses that infect protists have been discovered during the past decade. They are named giant viruses due to the large size of their viral particle (over 100 nm in diameter but up to 1.5 mu m) and to the extraordinary size of their genome, ranging from 150 kilobase pairs (kbp) to nearly 2.8 megabase pairs (Mbp). Their genomes, generally in the form of double-stranded DNA, may be linear or circular. They have been grouped into the nucleocytoplasmic large DNA virus (NCLDV) superfamily. The NCLDVs are divided into six families. Among these six viral families, three infect protozoa: the Mimiviridae and Marseilleviridae families infect amoebae and algae, and the newly discovered Pandoravirus salinus and P. dulcis, infect amoebae.