Identification and characterization of the intracellular poly-3-hydroxybutyrate depolymerase enzyme PhaZ of Sinorhizobium meliloti
| Autor: | David Capstick, Kathy N. Lam, Trevor C. Charles, Scott R. D. Clark, Maria A. Trainer, Alicja Zachertowska |
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| Rok vydání: | 2010 |
| Předmět: |
Microbiology (medical)
Root nodule Polyesters Mutant lcsh:QR1-502 Hydroxybutyrates macromolecular substances Plant Root Nodulation Plant Roots Microbiology lcsh:Microbiology 03 medical and health sciences chemistry.chemical_compound Bacterial Proteins Biosynthesis Symbiosis Research article Cloning Molecular 030304 developmental biology 2. Zero hunger chemistry.chemical_classification 0303 health sciences Rhizosphere Sinorhizobium meliloti biology 030306 microbiology Polysaccharides Bacterial technology industry and agriculture Computational Biology food and beverages biology.organism_classification Carbon Enzyme chemistry Biochemistry lipids (amino acids peptides and proteins) Carboxylic Ester Hydrolases Gene Deletion |
| Zdroj: | BMC Microbiology, Vol 10, Iss 1, p 92 (2010) BMC Microbiology |
| ISSN: | 1471-2180 |
| DOI: | 10.1186/1471-2180-10-92 |
| Popis: | Background S. meliloti forms indeterminate nodules on the roots of its host plant alfalfa (Medicago sativa). Bacteroids of indeterminate nodules are terminally differentiated and, unlike their non-terminally differentiated counterparts in determinate nodules, do not accumulate large quantities of Poly-3-hydroxybutyrate (PHB) during symbiosis. PhaZ is in intracellular PHB depolymerase; it represents the first enzyme in the degradative arm of the PHB cycle in S. meliloti and is the only enzyme in this half of the PHB cycle that remains uncharacterized. Results The S. meliloti phaZ gene was identified by in silico analysis, the ORF was cloned, and a S. meliloti phaZ mutant was constructed. This mutant exhibited increased PHB accumulation during free-living growth, even when grown under non-PHB-inducing conditions. The phaZ mutant demonstrated no reduction in symbiotic capacity; interestingly, analysis of the bacteroids showed that this mutant also accumulated PHB during symbiosis. This mutant also exhibited a decreased capacity to tolerate long-term carbon starvation, comparable to that of other PHB cycle mutants. In contrast to other PHB cycle mutants, the S. meliloti phaZ mutant did not exhibit any decrease in rhizosphere competitiveness; however, this mutant did exhibit a significant increase in succinoglycan biosynthesis. Conclusions S. meliloti bacteroids retain the capacity to synthesize PHB during symbiosis; interestingly, accumulation does not occur at the expense of symbiotic performance. phaZ mutants are not compromised in their capacity to compete for nodulation in the rhizosphere, perhaps due to increased succinoglycan production resulting from upregulation of the succinoglycan biosynthetic pathway. The reduced survival capacity of free-living cells unable to access their accumulated stores of PHB suggests that PHB is a crucial metabolite under adverse conditions. |
| Databáze: | OpenAIRE |
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