A better understanding of Earth's viruses thanks to metagenomes

Abstract

Despite their large number, viruses present in the environment remain largely unknown. Metagenomic approaches, targeting viruses specifically or not, have allowed us a better understanding of the composition of natural viral communities, with Caudoviricetes, Microviridae, Cressdnaviricota or Phycodnaviridae being the most frequently found viral groups. Metagenomes are gradually revealing the extent of the diversity of these groups and their structure, highlighting the large number of species, genera and even viral families, most of which being seen for the first time. Within these groups, the gene content, infected hosts and inhabited ecosystems are often consistent with the evolutionary history traced with marker genes. Thus, the diversity of viruses and their genes is more a reflection of their ancient origin and long coevolution with their hosts than of their ability to mutate rapidly.