Frontiers in Microbiology (Jul 2021)

Development of a Hyperosmotic Stress Inducible Gene Expression System by Engineering the MtrA/MtrB-Dependent NCgl1418 Promoter in Corynebacterium glutamicum

  • Jingwen Huang,
  • Jingwen Huang,
  • Jiuzhou Chen,
  • Yu Wang,
  • Tuo Shi,
  • Xiaomeng Ni,
  • Wei Pu,
  • Jiao Liu,
  • Yingyu Zhou,
  • Yingyu Zhou,
  • Ningyun Cai,
  • Shuangyan Han,
  • Ping Zheng,
  • Jibin Sun,
  • Jibin Sun

DOI
https://doi.org/10.3389/fmicb.2021.718511
Journal volume & issue
Vol. 12

Abstract

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Corynebacterium glutamicum is an important workhorse for industrial production of diversiform bioproducts. Precise regulation of gene expression is crucial for metabolic balance and enhancing production of target molecules. Auto-inducible promoters, which can be activated without expensive inducers, are ideal regulatory tools for industrial-scale application. However, few auto-inducible promoters have been identified and applied in C. glutamicum. Here, a hyperosmotic stress inducible gene expression system was developed and used for metabolic engineering of C. glutamicum. The promoter of NCgl1418 (PNCgl1418) that was activated by the two-component signal transduction system MtrA/MtrB was found to exhibit a high inducibility under hyperosmotic stress conditions. A synthetic promoter library was then constructed by randomizing the flanking and space regions of PNCgl1418, and mutant promoters exhibiting high strength were isolated via fluorescence activated cell sorting (FACS)-based high-throughput screening. The hyperosmotic stress inducible gene expression system was applied to regulate the expression of lysE encoding a lysine exporter and repress four genes involved in lysine biosynthesis (gltA, pck, pgi, and hom) by CRISPR interference, which increased the lysine titer by 64.7% (from 17.0 to 28.0 g/L) in bioreactors. The hyperosmotic stress inducible gene expression system developed here is a simple and effective tool for gene auto-regulation in C. glutamicum and holds promise for metabolic engineering of C. glutamicum to produce valuable chemicals and fuels.

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