title: Metabolomic basis of laboratory evolution of butanol tolerance in photosynthetic Synechocystis sp. PCC 6803.
abstract: BACKGROUND
  Recent efforts demonstrated the potential application of cyanobacteria as a "microbial cell factory" to produce butanol directly from CO2. However, cyanobacteria have very low tolerance to the toxic butanol, which limits the economic viability of this renewable system.
  
  
  RESULTS
  Through a long-term experimental evolution process, we achieved a 150% increase of the butanol tolerance in a model cyanobacterium Synechocystis sp. PCC 6803 after a continuous 94 passages for 395 days in BG11 media amended with gradually increased butanol concentration from 0.2% to 0.5% (v/v). To decipher the molecular mechanism responsible for the tolerance increase, we employed an integrated GC-MS and LC-MS approach to determine metabolomic profiles of the butanol-tolerant Synechocystis strains isolated from several stages of the evolution, and then applied PCA and WGCNA network analyses to identify the key metabolites and metabolic modules related to the increased tolerance. The results showed that unstable metabolites of 3-phosphoglyceric acid (3PG), D-fructose 6-phosphate (F6P), D-glucose 6-phosphate (G6P), NADPH, phosphoenolpyruvic acid (PEP), D-ribose 5-phosphate (R5P), and stable metabolites of glycerol, L-serine and stearic acid were differentially regulated during the evolution process, which could be related to tolerance increase to butanol in Synechocystis.
  
  
  CONCLUSIONS
  The study provided the first time-series description of the metabolomic changes related to the gradual increase of butanol tolerance, and revealed a metabolomic basis important for rational tolerance engineering in Synechocystis.
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering & Technology, Tianjin University, Tianjin, 300072, P.R. China. fengzongyiyepiao@qq.com.|Key Laboratory of Systems Bioengineering, Ministry of Education of China, Tianjin, 300072, P.R. China. fengzongyiyepiao@qq.com.|Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, P.R. China. fengzongyiyepiao@qq.com.
authors.forename: Yaxing
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering & Technology, Tianjin University, Tianjin, 300072, P.R. China. simon19891112@qq.com.|Key Laboratory of Systems Bioengineering, Ministry of Education of China, Tianjin, 300072, P.R. China. simon19891112@qq.com.|Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, P.R. China. simon19891112@qq.com.
authors.forename: Mengliang
authors.initials: M
authors.lastname: Shi
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering & Technology, Tianjin University, Tianjin, 300072, P.R. China. yadai0301@163.com.|Key Laboratory of Systems Bioengineering, Ministry of Education of China, Tianjin, 300072, P.R. China. yadai0301@163.com.|Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, P.R. China. yadai0301@163.com.
authors.forename: Xiangfeng
authors.initials: X
authors.lastname: Niu
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering & Technology, Tianjin University, Tianjin, 300072, P.R. China. zhangxiaoqingtju@163.com.|Key Laboratory of Systems Bioengineering, Ministry of Education of China, Tianjin, 300072, P.R. China. zhangxiaoqingtju@163.com.|Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, P.R. China. zhangxiaoqingtju@163.com.
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering & Technology, Tianjin University, Tianjin, 300072, P.R. China. gzero2013@163.com.|Key Laboratory of Systems Bioengineering, Ministry of Education of China, Tianjin, 300072, P.R. China. gzero2013@163.com.|Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, P.R. China. gzero2013@163.com.
authors.forename: Lianju
authors.initials: L
authors.lastname: Gao
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering & Technology, Tianjin University, Tianjin, 300072, P.R. China. lchen@tju.edu.cn.|Key Laboratory of Systems Bioengineering, Ministry of Education of China, Tianjin, 300072, P.R. China. lchen@tju.edu.cn.|Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, P.R. China. lchen@tju.edu.cn.
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering & Technology, Tianjin University, Tianjin, 300072, P.R. China. jwang88@tju.edu.cn.|Key Laboratory of Systems Bioengineering, Ministry of Education of China, Tianjin, 300072, P.R. China. jwang88@tju.edu.cn.|Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, P.R. China. jwang88@tju.edu.cn.
authors.forename: Jiangxin
authors.initials: J
authors.lastname: Wang
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering & Technology, Tianjin University, Tianjin, 300072, P.R. China. wwzhang8@tju.edu.cn.|Key Laboratory of Systems Bioengineering, Ministry of Education of China, Tianjin, 300072, P.R. China. wwzhang8@tju.edu.cn.|Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, P.R. China. wwzhang8@tju.edu.cn.
authors.forename: Weiwen
authors.initials: W
authors.lastname: Zhang
mesh_terms: D000440:Butanols / Q000378:metabolism*; D019020:Directed Molecular Evolution / Q000379:methods*; D046939:Synechocystis / Q000235:genetics / Q000378:metabolism
chemical_list: D000440:Butanols