This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Wang, C.
Right arrow Articles by Sobral, B. W. S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Wang, C.
Right arrow Articles by Sobral, B. W. S.

 Previous Article  |  Next Article 

Journal of Bacteriology, December 2007, p. 9050-9056, Vol. 189, No. 24
0021-9193/07/$08.00+0     doi:10.1128/JB.01190-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Influence of the Poly-3-Hydroxybutyrate (PHB) Granule-Associated Proteins (PhaP1 and PhaP2) on PHB Accumulation and Symbiotic Nitrogen Fixation in Sinorhizobium meliloti Rm1021{triangledown}

Chunxia Wang,1* Xiaoyan Sheng,1 Raymie C. Equi,1 Maria A. Trainer,2 Trevor C. Charles,2 and Bruno W. S. Sobral1

Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, Virginia 24061,1 Department of Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada2

Received 26 July 2007/ Accepted 25 September 2007

Sinorhizobium meliloti cells store excess carbon as intracellular poly-3-hydroxybutyrate (PHB) granules that assist survival under fluctuating nutritional conditions. PHB granule-associated proteins (phasins) are proposed to regulate PHB synthesis and granule formation. Although the enzymology and genetics of PHB metabolism in S. meliloti have been well characterized, phasins have not yet been described for this organism. Comparison of the protein profiles of the wild type and a PHB synthesis mutant revealed two major proteins absent from the mutant. These were identified by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) as being encoded by the SMc00777 (phaP1) and SMc02111 (phaP2) genes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins associated with PHB granules followed by MALDI-TOF confirmed that PhaP1 and PhaP2 were the two major phasins. Double mutants were defective in PHB production, while single mutants still produced PHB, and unlike PHB synthesis mutants that have reduced exopolysaccharide, the double mutants had higher exopolysaccharide levels. Medicago truncatula plants inoculated with the double mutant exhibited reduced shoot dry weight (SDW), although there was no corresponding reduction in nitrogen fixation activity. Whether the phasins are involved in a metabolic regulatory response or whether the reduced SDW is due to a reduction in assimilation of fixed nitrogen rather than a reduction in nitrogen fixation activity remains to be established.

* Corresponding author. Mailing address: Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA 24061. Phone: (540) 231-1958. Fax: (540) 231-2606. E-mail: cwang{at}vbi.vt.edu

{triangledown} Published ahead of print on 5 October 2007.

Journal of Bacteriology, December 2007, p. 9050-9056, Vol. 189, No. 24
0021-9193/07/$08.00+0     doi:10.1128/JB.01190-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»