title: Long-term continuous adaptation of Escherichia coli to high succinate stress and transcriptome analysis of the tolerant strain.
abstract: To understand the responses of Escherichia coli to high succinate stress and to determine the roles of upregulated genes in high succinate tolerance, a continuous culture of wild-type E. coli W3110 was performed for 268 days in a gradually increasing concentration of succinate. Growth of the final adapted strain, designated DST160, proceeded growth rate of 0.20 h(-1) without a lag phase in medium containing 0.592 M succinate, while the wild-type strain showed 0.02 h(-1) in 38 h. The growth rates of DST160 in media containing either 0.61 M NaCl, 0.61 M KCl, or at pH 4.5 were 25% higher, 18% lower, and 57% higher than those of wild-type, respectively, implying DST160 acquired salt tolerance and pH shock tolerance as well as succinate tolerance. DNA microarray and real-time PCR results indicated that genes controlling active transport and biosynthesis of osmoprotectants were upregulated in DST160 compared to W3110. When ygjE, encoding a putative tartrate/succinate antiporter, and betA, encoding betaine biosynthesis, were expressed in a wild-type E. coli as represent genes for active transport and osmoprotectant synthesis, respectively, greater growth rates were achieved under 0.592 M succinate stress conditions (seven times higher due to ygjE expression and six times higher due to betA expression) than wild-type. The potential to design a metabolic engineering for microbial succinate production is suggested based on the transcriptional regulation of the long-term adapted DST160.
authors.affiliation: Department of Biotechnology, Catholic University of Korea, Bucheon, Gyeonggi 420-743, Republic of Korea.
authors.forename: Yeong-Deok
authors.initials: YD
authors.lastname: Kwon
authors.forename: Susie
authors.initials: S
authors.lastname: Kim
authors.forename: Sang Yup
authors.initials: SY
authors.lastname: Lee
authors.forename: Pil
authors.initials: P
authors.lastname: Kim
mesh_terms: D000222:Adaptation, Physiological; D003470:Culture Media; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction; D012965:Sodium Chloride / Q000494:pharmacology; D019802:Succinic Acid / Q000737:chemistry*
chemical_list: D003470:Culture Media; D029968:Escherichia coli Proteins; D012965:Sodium Chloride; D019802:Succinic Acid