Ten reasons to exclude viruses from the tree of life

Abstract

When viruses were discovered, they were accepted as missing links between the inert world and living organisms. However, this idea was soon abandoned as information about their molecular parasitic nature accumulated. Recently, the notion that viruses are living organisms that have had a role in the evolution of some essential features of cells has experienced a renaissance owing to the discovery of unusually large and complex viruses that possess typical cellular genes. Here, we contend that there is strong evidence against the notion that viruses are alive and represent ancient lineages of the tree of life.

There is no such thing as a tree of life (and of course viruses are out!)

“…Microbiol. 7, 306-311 (2009)) 1 as a decalogue on the position of giant viruses in the tree of life, mainly directed against our work on Mimivirus 2 . My opinion is that, according to K. Popper 3 , this reaction is more religious than scientific, and more the result of deductions than observed data.…”

Understanding viruses: Philosophical investigations

“…has been raised repeatedly throughout the history of Scola et al, 2008), had the potential to radically modify our views about the living or nonliving status of viruses (mainly because it has become very difficult to draw a boundary between some cellular organisms strongly dependent on their host and harbouring less than a minimal genome and the giant viruses that encode many genes and exhibit some degree of autonomy (Claverie & Abergel, 2010; this special issue)) and/or the role viruses could have played in the origins of life (Forterre, 2010b;Raoult & Forterre, 2008). These views have been met with scepticism by many other virologists (López-García, 2012; López-García & Moreira, 2012;Moreira & López-García, 2009), giving rise to a strong controversy (see, e.g., (Villarreal, 2004), (Villarreal & Witzany, 2010); see also Claverie and Abergel, Forterre, as well as van Regenmortel, this special issue).…”

“…Viruses also successfully occupy a wide range of niches, are key players in evolutionary and ecological processes (Villarreal 2005;Wasik and Turner 2013), and, last but not least, have long been a matter of concern to medical doctors and epidemiologists. The situation is even more astonishing considering that several biologists have, over the years, produced a rich conceptual reflection on viruses (e.g., Burnet, 1945;Claverie & Abergel, 2010Forterre, 2010a;Koonin & Dolja, 2013;López-García, 2012;Lwoff, 1957;Moreira & López-García, 2009;Raoult & Forterre, 2008;Stanley, 1957;Van Regenmortel, 2003), and the philosophy of microbiology more broadly has blossomed in recent years (O'Malley, 2013(O'Malley, , 2014O'Malley & Dupré, 2007a, 2007b. Meanwhile, both virologists and historians of biology have produced a detailed and rich history of virology (e.g., Bos, 1999Bos, , 2000Creager, 2002;Hughes, 1977;Lustig & Levine, 1992;Sankaran, 2010;Summers, 2014;van Helvoort, 1994avan Helvoort, , 1994bvan Helvoort, , 1996Waterson & Wilkinson, 1978) 1 .…”

Senomic view of the cell: Senome versus Genome

“…A very strong argument in a favour of the Senome for the still mysterious phenomenon of life is provided by viruses which are inert non-living structures as long as they are outside of their host cells [93]. However when inside their host cells and included within the senomic context, viruses can actively manipulate cellular membranes and the cytoskeleton.…”