Experimental Evolution of Ultraviolet Radiation Resistance in Escherichia Coli

Abstract

Ultraviolet (UV) light is a major cause of stress, mutation, and mortality in microorganisms, causing numerous forms of cellular damage. Nevertheless, there is tremendous variation within and among bacterial species in their sensitivity to UV light. We investigated direct and correlated responses to selection during exposure to UV. Replicate lines of Escherichia coli K12 were propagated for 600 generations, half with UV and half as a control without UV. All lines responded to selection, and we found strong positive and negative correlated responses to selection associated with increased UV resistance. Compared to Control populations, UV-selected populations increased in desiccation and starvation resistance approximately twofold but were 10 times more sensitive to hypersalinity. There was little evidence for a persistent large competitive fitness cost to UV resistance. These results suggest that natural variation in UV resistance may be maintained by trade-offs for resistance to other abiotic sources of mortality. We observed an average twofold increase in cell size by the UV-selected populations, consistent with a structural mode of adaptation to UV exposure having preadaptive and maladaptive consequences to other abiotic stresses.

Building upon current knowledge and techniques of indoor microbiology to construct the next era of theory into microorganisms, health, and the built environment

“…A large body of research has been conducted on the effect of full-spectrum (sunlight) light [141,150,151], ultraviolet light [147,[152][153][154][155][156], and blue or red wavelengths [157][158][159][160], on mono-cultured bacterial or fungal survival and activity ( Fig. 1).…”

“…Additionally, light has been shown to reduce virus virulence and increase viron decay [103,141,161]. However, microorganisms, particularly bacteria, may easily evolve resistance to UVA and UVB light exposure [153]. UVC light to control microbial growth has recently gained popularity because there is no a priori resistance to it, as it does not penetrate the atmosphere.…”

Rapid evolution of antioxidant defence in a natural population of Daphnia magna

“…carbonyl‐ or peroxide‐containing metabolites) produced by oxidative stress (Hayes & Pulford, ). Few previous studies have tested how populations track UVR levels through time and these all relied on experimental evolution showing an increased UV resistance when bacteria were exposed to higher UVR levels in the laboratory (Goldman & Travisano, ; Wassmann et al ., ). As far as we know, no studies explored whether and how UV resistance and the associated physiological defence evolve in natural populations where changes in other abiotic and biotic factors are likely to occur.…”

An examination of fitness costs of glyphosate resistance in the common morning glory, Ipomoea purpurea

“…A transgenic design is perhaps the best experimental strategy to identify costs; however, such strategy is experimentally restricted to model plant species and has yet to be replicated in an agricultural weed. Artificial selection, on the other hand, is a tool that has been broadly used in evolutionary ecologyfrom studies that examine the evolution of plant mating systems to studies that consider parasitoid and pesticide resistance in Drosophila and Daphnia magna, respectively (Worley and Barrett 2000;Kraaijeveld et al 2002;Delph et al 2004;Conner et al 2011;Goldman and Travisano 2011;Jansen et al 2011). Surprisingly, few herbicide resistance studies have used designs similar to those used in evolutionary ecology wherein randomly cross-pollinated groups are utilized as controls and both increased and decreased resistance lines are generated.…”