tolerance or scavenging of nutrients to support the growth of new biomass. Fitness trajectories of select lineages clearly indicate that adaptive improvements under UVR and non-UVR conditions were acquired preferentially and differentially contributed to relative fitness under varied growth conditions. The results of this study lend support to our earlier observations that suggest increased mutation rate in the form of inducible mutability does not impede adaptation by mutation accumulation. Rather, UVR and non-UVR lineages preferentially acquired adaptive growth improvements in a similar manner and additional fitness gains by UVR lineages may have been due to greater access to beneficial mutations. Our future work will compare the influence of different mechanisms of mutability on adaptation in an advanced genetic system equipped with genomic tools for analysis. Supporting Information Table S1 Doubling time of population samples and isolates from lineages of P. cichorii 302959 during growth under non-UVR and UVR conditions. (DOCX) References 1. De Visser JAGM, Rozen DE (2005) Limits to adaptation in asexual populations. J Evol Biol 18: 779–788. 2. De Visser JAGM (2002) The fate of microbial mutators. Microbiology 148: 1247–1252. 3. Sundin GW, Weigand MR (2007) The microbiology of mutability. FEMS Microbiol Lett 277: 11–20. 4. Hall LMC, Henderson-Begg SK (2006) Hypermutable bacteria isolated from humans – a critical analysis. Microbiology 152: 2505–2514. 5. Giraud A, Radman M, Matic I, Taddei R (2001) The rise and fall of mutator bacteria. Curr Opin Microbiol 4: 582–585. 6. Tenaillon O, Taddei F, Radman M, Matic I (2001) Second order selection in bacterial evolution: selection acting on mutation and recombination rates in the course of adaptation. Res Microbiol 152: 11–16. 7. Schlacher K, Goodman MF (2007) Lessons from 50 years of SOS DNA- damage-induced mutagenesis. Nat Rev Mol Cell Biol 8: 587–594. 8. Courcelle J, Khodursky A, Peter B, Brown PO, Hanawalt PC (2001) Comparative gene expression profiles following UV exposure in wild-type and SOS-deficient Escherichia coli. Genetics 158: 41–64. 9. Jarosz DF, Beuning PJ, Cohen SE, Walker GC (2007) Y-family DNA polymerases in Escherichia coli. Trends Microbiol 15: 70–77. 10. Kim JJ, Sundin GW (2000) Regulation of the rulAB mutagenic DNA repair operon of Pseudomonas syringae by UV-B (290 to 320 nanometers) radiation and analysis of rulAB-mediated mutability in vitro and in planta. J Bacteriol 182: 6137–44. 11. Sundin GW, Murillo J (1999) Functional analysis of the Pseudomonas syringae rulAB determinant in tolerance to ultraviolet B (290–320 nm) radiation and distribution of rulAB among P. syringae pathovars. Environ Microbiol 1: 75–87. 12. Weigand MR, Sundin GW (2009) Long-term effects of inducible mutagenic DNA repair on relative fitness and phenotypic diversification in Pseudomonas cichorii 302959. Genetics 181: 199–208. 13. Zhang S, Sundin GW (2004) Mutagenic DNA repair potential in Pseudomonas spp., and characterization of the rulABPc operon from the highly mutable strain Pseudomonas cichorii 302959. Can J Microbiol 50: 29–39. 14. Loh E, Salk JJ, Loeb LA (2010) Optimization of DNA polymerase mutation rates during bacterial evolution. Proc Natl Acad Sci USA 107: 1154–1159. 15. MacLean RC, Bell G, Rainey PB (2004) The evolution of a pleiotropic fitness tradeoff in Pseudomonas fluorescens. Proc Natl Acad Sci USA 101: 8072–8077. Inducible Mutability and Components of Adaptation Table S2 Lag time of population samples and isolates from lineages of P. cichorii 302959 during growth under non-UVR and UVR conditions. (DOCX) Table S3 Percent survival of population samples and isolates from lineages of P. cichorii 302959 following ,140 J m22 UVC. (DOCX) Acknowledgments The authors thank Rich Lenski, Tom Schmidt, and Barb Sears for helpful comments. Author Contributions Conceived and designed the experiments: MRW GWS. Performed the experiments: MRW VNT. Analyzed the data: MRW VNT. Contributed reagents/materials/analysis tools: MRW VNT GWS. Wrote the paper: MRW GWS. 16. Cooper VS, Lenski RE (2000) The population genetics of ecological specialization in evolving Escherichia coli populations. Nature 407: 736–739. 17. King EO, Ward MK, Raney DC (1954) Two simple media for the demonstration of pyocyanin and fluorescin. J Lab Clin Med 44: 310–307. 18. Choi KH, Kumar A, Scheizer HP (2006) A 10-min method for preparation of highly electrocompetent Pseudomonas aeruginosa cells: application for DNA fragment transfer between chromosomes and plasmid transformation. J Microbiol Meth 64: 391–397. 19. Sambrook J, Fritsch EF, Maniatis T (1989) Molecular Clonging: A Laboratory Manual. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press. 20. Lenski RE, Souza V, Duong LP, Phan QG, Nguyen TNM, et al. (1994) Epistatic effects of promoter and repressor functions of the Tn10 tetracycline-resistance operon on the fitness of Escherichia coli. Mol Ecol 3: 127–135. 21. Madigan MT, Martinko JM (2006) Brock Biology of Microorganisms, 11th Edition. Upper Saddle River, NJ: Prentice Hall. 148 p. 22. Sleight SC, Lenski RE (2007) Evolutionary adaptation to freeze-thaw-growth cycles in Escherichia coli. Physiol Biochem Zool 80: 370–385. 23. Lenski RE, Mongold JA, Sniegowski PD, Travisano M, Vasi F, et al. (1998) Evolution of competitive fitness in experimental populations of E. coli: What makes one genotype a better competitor than another? Antonie van Leeuwenhoek 73: 35–47. 24. Shimoni Y, Altuvia S, Margalit H, Biham O (2009) Stochastic analysis of the SOS response in Escherichia coli. PLoS ONE 4: e5363. 25. Friedman N, Vardi S, Ronen M, Alon U, Stavans J (2005) Precise temporal modulation in the response of the SOS DNA repair network of individual bacteria. PLoS Biol 3: 1261–1268. 26. Finkel SE (2006) Long-term survival during stationary phase: evolution and the GASP phenotype. Nat Rev Microbiol 4: 113–119. 27. Turner PE, Souza V, Lenski RE (1996) Tests of ecological mechanisms promoting the stable coexistence of two bacterial genotypes. Ecology 77: 2119–2129. 28. Elena SF, Cooper VS, Lenski RE (1996) Punctuated evolution caused by selection of rare beneficial mutations. Science 272: 1802–1804. 29. MacLean RC (2005) Adaptive radiation in microbial microcosms. J Evol Biol 18: 1376–1386. 30. Travisano M, Lenski RE (1996) Long-term experimental evolution in Escherichia coli IV. Targets of Selection and the specificity of adaptation. Genetics 143: 15–26. PLoS ONE | www.plosone.org 12 January 2011 | Volume 6 | Issue 1 | e15975