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Journal of Bacteriology, June 2008, p. 4173-4180, Vol. 190, No. 12
0021-9193/08/$08.00+0     doi:10.1128/JB.00134-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Genetic and Biochemical Characterization of the Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) Synthase in Haloferax mediterranei{triangledown} ,{dagger}

Qiuhe Lu,1,2,{ddagger} Jing Han,1,2,{ddagger} Ligang Zhou,1,2 Jian Zhou,1 and Hua Xiang1*

State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences,1 Graduate University of Chinese Academy of Sciences, Beijing, Peoples Republic of China2

Received 25 January 2008/ Accepted 31 March 2008

The haloarchaeon Haloferax mediterranei has shown promise for the economical production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a desirable bioplastic. However, little is known at present about the genes involved in PHBV synthesis in the domain Archaea. In this study, we cloned the gene cluster (phaECHme) encoding a polyhydroxyalkanoate (PHA) synthase in H. mediterranei CGMCC 1.2087 via thermal asymmetric interlaced PCR. Western blotting revealed that the phaEHme and phaCHme genes were constitutively expressed, and both the PhaEHme and PhaCHme proteins were strongly bound to the PHBV granules. Interestingly, CGMCC 1.2087 could synthesize PHBV in either nutrient-limited medium (supplemented with 1% starch) or nutrient-rich medium, up to 24 or 18% (wt/wt) in shaking flasks. Knockout of the phaECHme genes in CGMCC 1.2087 led to a complete loss of PHBV synthesis, and only complementation with the phaECHme genes together (but not either one alone) could restore to this mutant the capability for PHBV accumulation. The known haloarchaeal PhaC subunits are much longer at their C termini than their bacterial counterparts, and the C-terminal extension of PhaCHme was proven to be indispensable for its function in vivo. Moreover, the mixture of purified PhaEHme/PhaCHme (1:1) showed significant activity of PHA synthase in vitro. Taken together, our results indicated that a novel member of the class III PHA synthases, composed of PhaCHme and PhaEHme, accounted for the PHBV synthesis in H. mediterranei.

* Corresponding author. Mailing address: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Datun Road, Chaoyang District, Beijing 100101, Peoples Republic of China. Phone and fax: (86) 10-6480-7472. E-mail: xiangh{at}sun.im.ac.cn

{triangledown} Published ahead of print on 11 April 2008.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

{ddagger} Q.L. and J.H. contributed equally to this paper.

Journal of Bacteriology, June 2008, p. 4173-4180, Vol. 190, No. 12
0021-9193/08/$08.00+0     doi:10.1128/JB.00134-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Han, J., Lu, Q., Zhou, L., Liu, H., Xiang, H. (2009). Identification of the Polyhydroxyalkanoate (PHA)-Specific Acetoacetyl Coenzyme A Reductase among Multiple FabG Paralogs in Haloarcula hispanica and Reconstruction of the PHA Biosynthetic Pathway in Haloferax volcanii. Appl. Environ. Microbiol. 75: 6168-6175 [Abstract] [Full Text]  
  • Jahns, A. C., Rehm, B. H. A. (2009). Tolerance of the Ralstonia eutropha Class I Polyhydroxyalkanoate Synthase for Translational Fusions to Its C Terminus Reveals a New Mode of Functional Display. Appl. Environ. Microbiol. 75: 5461-5466 [Abstract] [Full Text]  
  • Jendrossek, D. (2009). Polyhydroxyalkanoate Granules Are Complex Subcellular Organelles (Carbonosomes). J. Bacteriol. 191: 3195-3202 [Full Text]  


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