These giant viruses have more protein-making gear than any known virus

Two newly discovered giant viruses have the most comprehensive toolkit for assembling proteins found in any known virus. In a host cell, the viruses have the enzymes needed to wrangle all 20 standard amino acids, the building blocks of life.

Researchers dubbed the viruses Tupanvirus deep ocean and Tupanvirus soda lake, combining the name of the indigenous South American god of thunder, Tupan, with the extreme environment where each type of virus was found. The giant viruses are among the largest of their kind — up to 2.3 micrometers in length — which is about 23 times as long as a particle of HIV, the scientists report February 27 in Nature Communications.  

Tupanviruses can infect a wide range of hosts, such as protists and amoebas, but pose no threat to humans, the researchers say.

Viruses are considered nonliving, but the genetic complexity of giant viruses has some scientists questioning that categorization. Each Tupanvirus, for example, has a massive genetic instruction book with roughly 1.5 million base pairs of DNA, more than what some bacteria have, says coauthor Bernard La Scola, a virologist at Aix-Marseille University in France.

But other scientists say giant viruses aren’t so different from their smaller kin. Research by Frederik Schulz, with the Department of Energy Joint Genome Institute in Walnut Creek, Calif., suggests these microscopic behemoths are regular viruses that acquired extra genes from hosts and should not be classified as life.

Tupanviruses don’t settle the controversy, but they do challenge our preconceptions of what life is, La Scola says.

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Editor’s note: This story was updated February 28, 2018 to correct how Tupanviruses interact with amino acids.