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Journal of Bacteriology, November 1999, p. 6656-6663, Vol. 181, No. 21
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Acetate Metabolism in a pta Mutant of Escherichia coli W3110: Importance of Maintaining Acetyl Coenzyme A Flux for Growth and Survival

Dong-Eun Chang,1,2 Sooan Shin,1,dagger Joon-Shick Rhee,2 and Jae-Gu Pan1,*

Bioprocess Engineering Division, Korea Research Institute of Bioscience and Biotechnology, Yusong, Taejon 305-600,1 and Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Yusong, Taejon 305-701,2 Korea

Received 3 May 1999/Accepted 12 August 1999

In order to study the physiological role of acetate metabolism in Escherichia coli, the growth characteristics of an E. coli W3100 pta mutant defective in phosphotransacetylase, the first enzyme of the acetate pathway, were investigated. The pta mutant grown on glucose minimal medium excreted unusual by-products such as pyruvate, D-lactate, and L-glutamate instead of acetate. In an analysis of the sequential consumption of amino acids by the pta mutant growing in tryptone broth (TB), a brief lag between the consumption of amino acids normally consumed was observed, but no such lag occurred for the wild-type strain. The pta mutant was found to grow slowly on glucose, TB, or pyruvate, but it grew normally on glycerol or succinate. The defective growth and starvation survival of the pta mutant were restored by the introduction of poly-beta -hydroxybutyrate (PHB) synthesis genes (phbCAB) from Alcaligenes eutrophus, indicating that the growth defect of the pta mutant was due to a perturbation of acetyl coenzyme A (CoA) flux. By the stoichiometric analysis of the metabolic fluxes of the central metabolism, it was found that the amount of pyruvate generated from glucose transport by the phosphoenolpyruvate-dependent phosphotransferase system (PTS) exceeded the required amount of precursor metabolites downstream of pyruvate for biomass synthesis. These results suggest that E. coli excretes acetate due to the pyruvate flux from PTS and that any method which alleviates the oversupply of acetyl CoA would restore normal growth to the pta mutant.

* Corresponding author. Mailing address: Bioprocess Engineering Division, Korea Research Institute of Bioscience and Biotechnology (KRIBB), P.O. Box 115, Yusong, Taejon 305-600, Korea. Phone: 82-42-860-4483. Fax: 82-42-860-4594. E-mail: jgpan{at}kribb4680.kribb.re.kr.

dagger Present address: Center for Vaccine Development, School of Medicine, University of Maryland, Baltimore, MD 21201.

Journal of Bacteriology, November 1999, p. 6656-6663, Vol. 181, No. 21
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.


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