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Applied and Environmental Microbiology, June 2002, p. 2943-2949, Vol. 68, No. 6
0099-2240/02/$04.00+0     DOI: 10.1128/AEM.68.6.2943-2949.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Identification and Isolation of Genes Involved in Poly(ß-Hydroxybutyrate) Biosynthesis in Azospirillum brasilense and Characterization of a phbC Mutant

Daniel Kadouri, Saul Burdman, Edouard Jurkevitch, and Yaacov Okon^*

Department of Plant Pathology and Microbiology and The Otto Warburg Center for Agricultural Biotechnology, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel

Received 27 November 2001/ Accepted 29 March 2002

Like many other prokaryotes, rhizobacteria of the genus Azospirillum produce high levels of poly(ß-hydroxybutyrate) (PHB) under suboptimal growth conditions. Utilization of PHB by bacteria under stress has been proposed as a mechanism that favors their compatible establishment in competitive environments, thus showing great potential for the improvement of bacterial inoculants for plants and soils. The three genes that are considered to be essential in the PHB biosynthetic pathway, phbA (ß-ketothiolase), phbB (acetoacetyl coenzyme A reductase), and phbC (PHB synthase), were identified in Azospirillum brasilense strain Sp7, cloned, and sequenced. The phbA, -B, and -C genes were found to be linked together and located on the chromosome. An A. brasilense phbC mutant was obtained by insertion of a kanamycin resistance cassette within the phbC gene. No PHB production was detected in this mutant. The capability of the wild-type strain to endure starvation conditions was higher than that of the mutant strain. However, motility, cell aggregation, root adhesion, and exopolysaccharide (EPS) and capsular polysaccharide (CPS) production were higher in the phbC mutant strain than in the wild type.

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* Corresponding author. Mailing address: Department of Plant Pathology and Microbiology, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel. Phone: 972 8 9489216. Fax: 972 8 9466794. E-mail: okon{at}agri.huji.ac.il.

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Applied and Environmental Microbiology, June 2002, p. 2943-2949, Vol. 68, No. 6
0099-2240/02/$04.00+0     DOI: 10.1128/AEM.68.6.2943-2949.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

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