Phenotypic convergence in bacterial adaptive evolution to ethanol stress.
BACKGROUND
Bacterial cells have a remarkable ability to adapt to environmental changes, a phenomenon known as adaptive evolution. During adaptive evolution, phenotype and genotype dynamically changes; however, the relationship between these changes and associated constraints is yet to be fully elucidated.


RESULTS
In this study, we analyzed phenotypic and genotypic changes in Escherichia coli cells during adaptive evolution to ethanol stress. Phenotypic changes were quantified by transcriptome and metabolome analyses and were similar among independently evolved ethanol tolerant populations, which indicate the existence of evolutionary constraints in the dynamics of adaptive evolution. Furthermore, the contribution of identified mutations in one of the tolerant strains was evaluated using site-directed mutagenesis. The result demonstrated that the introduction of all identified mutations cannot fully explain the observed tolerance in the tolerant strain.


CONCLUSIONS
The results demonstrated that the convergence of adaptive phenotypic changes and diverse genotypic changes, which suggested that the phenotype-genotype mapping is complex. The integration of transcriptome and genome data provides a quantitative understanding of evolutionary constraints.
Quantitative Biology Center (QBiC), RIKEN, 6-2-3 Furuedai, Suita, Osaka, 565-0874, Japan. takaaki_horinouchi@riken.jp.
Takaaki
T
Horinouchi
Quantitative Biology Center (QBiC), RIKEN, 6-2-3 Furuedai, Suita, Osaka, 565-0874, Japan. ssuzuki@riken.jp.
Shingo
S
Suzuki
Department of Bioengineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8501, Japan. thirasawa@bio.titech.ac.jp.|Graduate School of Information Science and Technology, Osaka University, 1-5 Yamada-oka, Suita, Osaka, 565-0871, Japan. thirasawa@bio.titech.ac.jp.
Takashi
T
Hirasawa
Graduate School of Information Science, Nara Institute of Science and Technology, Ikoma, Nara, 630-0192, Japan. nono@is.naist.jp.
Naoaki
N
Ono
Graduate School of Information Science and Technology, Osaka University, 1-5 Yamada-oka, Suita, Osaka, 565-0871, Japan. yomo@ist.osaka-u.ac.jp.|Graduate School of Frontier Biosciences, Osaka University, 1-5 Yamada-oka, Suita, Osaka, 565-0871, Japan. yomo@ist.osaka-u.ac.jp.
Tetsuya
T
Yomo
Graduate School of Information Science and Technology, Osaka University, 1-5 Yamada-oka, Suita, Osaka, 565-0871, Japan. shimizu@ist.osaka-u.ac.jp.
Hiroshi
H
Shimizu
Quantitative Biology Center (QBiC), RIKEN, 6-2-3 Furuedai, Suita, Osaka, 565-0874, Japan. chikara.furusawa@riken.jp.|Graduate School of Information Science and Technology, Osaka University, 1-5 Yamada-oka, Suita, Osaka, 565-0871, Japan. chikara.furusawa@riken.jp.
Chikara
C
Furusawa
D005075:Biological Evolution; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D000431:Ethanol / Q000494:pharmacology*; D020869:Gene Expression Profiling; D009154:Mutation; D010641:Phenotype
D000431:Ethanol