A common, non-optimal phenotypic endpoint in experimental adaptations of bacteriophage lysis time
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1471-2148-12-37.pdf
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Author(s)
Heineman, Richard H.
Chantranupong, Lynne
Date Issued
March 2012
Journal
BMC Evolutionary Biology
Publisher
Springer (Biomed Central Ltd.)
Citation
Chantranupong, Lynne, and Richard H Heineman. “A Common, Non-optimal Phenotypic Endpoint in Experimental Adaptations of Bacteriophage Lysis Time.” BMC Evolutionary Biology 12.1 (2012): 37. Web. 13 Apr. 2012.
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Final published version
Abstract
Background: Optimality models of evolution, which ignore genetic details and focus on natural selection, are widely used but sometimes criticized as oversimplifications. Their utility for quantitatively predicting phenotypic evolution can be tested experimentally. One such model predicts optimal bacteriophage lysis interval, how long a virus should produce progeny before lysing its host bacterium to release them. The genetic basis of this life history trait is well studied in many easily propagated phages, making it possible to test the model across a variety of environments and taxa.
Results: We adapted two related small single-stranded DNA phages, ΦX174 and ST-1, to various conditions. The model predicted the evolution of the lysis interval in response to host density and other environmental factors. In all cases the initial phages lysed later than predicted. The ΦX174 lysis interval did not evolve detectably when the phage was adapted to normal hosts, indicating complete failure of optimality predictions. ΦX174 grown on slyD-defective hosts which initially entirely prevented lysis readily recovered to a lysis interval similar to that attained on normal hosts. Finally, the lysis interval still evolved to the same endpoint when the environment was altered to delay optimal lysis interval. ST-1 lysis interval evolved to be ~2 min shorter, qualitatively in accord with predictions. However, there were no changes in the single known lysis gene. Part of ST-1's total lysis time evolution consisted of an earlier start to progeny production, an unpredicted phenotypic response outside the boundaries of the optimality model.
Conclusions: The consistent failure of the optimality model suggests that constraint and genetic details affect quantitative and even qualitative success of optimality predictions. Several features of ST-1 adaptation show that lysis time is best understood as an output of multiple traits, rather than in isolation.
Keywords: Experimental evolution; ΦX174; Optimality; Life history evolution; Genetic constraint; Bacteriophage; Lysis; Molecular evolution; Virulence; Phenotype prediction
MIT Department
Massachusetts Institute of Technology. Department of Biology
Massachusetts Institute of Technology. Department of Chemical Engineering
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DOI of Published Version
https://doi.org/10.1186/1471-2148-12-37
