Fraction of spontaneous mutations that are deleterious

Range >60 %
Organism Vesicular stomatitis Indiana virus
Reference Duffy S, Shackelton LA, Holmes EC. Rates of evolutionary change in viruses: patterns and determinants. Nat Rev Genet. 2008 Apr9(4):267-76 p.272 right column bottom paragraphPubMed ID18319742
Primary Source [72] Sanjuan, R., Moya, A. & Elena, S. F. The distribution of fitness effects caused by single-nucleotide substitutions in an RNA virus. Proc. Natl Acad. Sci. USA 101, 8396–8401 (2004). DOI: 10.1073/pnas.0400146101PubMed ID15159545
Method Primary source abstract: "Here, [investigators] used site-directed mutagenesis to create 91 single mutant clones of vesicular stomatitis virus derived from a common ancestral cDNA and performed competition experiments to measure the relative fitness of each mutant."
Comments P.272 right column bottom paragraph: "Optimizing mutation rates. In any genetic system most mutations are deleterious (refs 1, 71) and viruses are no exception for example, more than 60% of spontaneous mutations in vesicular stomatitis virus (VSV) were found to be deleterious (primary source). In theory, natural selection should favour a reduction in mutation rates in static environments to reduce this burden of deleterious mutation (although non-zero mutation rates might still be optimal (ref 73)). However, viruses rarely experience a static environment, particularly as they often struggle against both innate and adaptive host immunity. As such, viruses probably always experience selection for non-zero mutation rates (ref 74). Therefore, the upper limit on mutation rate is a product of factors such as natural selection, genomic architecture (ref 75) and the ability to avoid loss of viability (ref 24) and/or genetic information (ref 76)."
Entered by Uri M
ID 112777