Editorial: Viruses, Genetic Exchange, and the Tree of Life

Overview & Synopsis

Editorial on the Research Topic Viruses, Genetic Exchange, and the Tree of Life We live in exciting times for microbiology research. The significant technological and scientific advancements in the past decades have now enabled scientists to pursue discovery and description of novel microbial and viral linages from previously uncharted Earth habitats. Two such discoveries are particularly exciting and noteworthy in this regard. First, the discovery of the first "giant virus, " Acanthamoeba polyphaga mimivirus, in 2003, and several others thereafter, posed intriguing questions regarding virus origins, evolution, classification, and their place in the "tree of life." Second, the discoveries of "Lokiarchaeota" and several other closely-related archaeal members that encode several eukaryote-specific proteins challenged the three-domain canonical structure of the tree of life. These discoveries have reopened debates on central questions in evolutionary biology research such as the origin of viruses, the origin of eukaryotes, evolutionary relationship between Archaea and Eukarya, and the structure and topology of the tree of life. In this Research Topic, we received a broad range of contributions addressing these and other related questions. Moelling and Broecker discussed the "virus first" model for the evolution of life on Earth. They provided several examples of virus diversity and abundance in a range of Earth environments and in the mammalian genomes. According to their view, ribozymes and viroids could have started early evolution albeit they also acknowledged competing alternatives such as the "proteins first" and the "metabolism first" scenarios of origins of life. In a separate contribution from the same authors,