The Plasticity of Cyanobacterial Metabolism Supports Direct CO2 Conversion to Ethylene

Wei Xiong, John A. Morgan, Justin Ungerer, Bo Wang, Pin Ching Maness, Jianping Yu

Research output: Contribution to journalArticlepeer-review

141 Scopus Citations

Abstract

The cyanobacterial tricarboxylic acid (TCA) cycle functions in both in biosynthesis and energy generation. However, it has until recently been generally considered to be incomplete1,2 with limited flux3, 4, and few attempts have been made to draw carbon from the cycle for biotechnological purposes. We demonstrated that ethylene can be sustainably and efficiently produced from the TCA cycle of the recombinant cyanobacterium Synechocystis 6803 expressing the Pseudomonas ethylene-forming enzyme (Efe)5. A new strain with a modified ribosome binding site upstream of the efe gene diverts 10% of fixed carbon to ethylene and shows increased photosynthetic activities. The highest specific ethylene production rate reached 718 ± 19 μ11-1 h-1 per A730 nm. Experimental and computational analyses based on kinetic 13C-isotope tracer and liquid chromatography coupled with mass spectrometry (LC-MS) demonstrated that the TCA metabolism is activated by the ethylene forming reaction, resulting in a predominantly cyclic architecture. The outcome significantly enhanced flux through the remodelled TCA cycle (37% of total fixed carbon) compared with a complete, but bifurcated and low-flux (13% of total fixed carbon) TCA cycle in the wild type. Global carbon flux is redirected towards the engineered ethylene pathway. The remarkable metabolic network plasticity of this cyanobac-terium is manifested by the enhancement of photosynthetic activity and redistribution of carbon flux, enabling efficient ethylene production from the TCA cycle.

Original languageAmerican English
Article numberArticle No. 15053
JournalNature Plants
Volume1
Issue number5
DOIs
StatePublished - May 2015

Bibliographical note

Publisher Copyright:
© 2015 Macmillan Publishers Limited. All rights reserved.

NREL Publication Number

  • NREL/JA-2700-62133

Keywords

  • algae
  • cyanobacteria
  • ethylene
  • kinetic 13C-labeling
  • liquid chromatography-mass spectrometry (LC-MS)
  • metabolic flux analysis
  • metabolomics
  • Synechocystis sp. 6803

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