Document Detail

Biosynthesis of branched-chain amino acids is essential for effective symbioses between beta-rhizobia and Mimosa pudica.
MedLine Citation:
PMID:  22556357     Owner:  NLM     Status:  Publisher    
Burkholderia phymatum STM815 and Cupriavidus taiwanensis LMG19424 are Betaproteobacterial strains that can effectively nodulate several species of the large legume genus Mimosa. A Tn5 mutant, derived from B. phymatum STM815 (KM60), and another derived from C. taiwanensis LMG19424 (KM184-55) induced Fix- nodules on Mimosa pudica. The Tn5-interrupted genes of the mutants showed strong homologies to ilvE which encodes a branched-chain amino acid aminotransferase and leuC which encodes the large subunit of isopropylmalate isomerase. Both enzymes are known to be involved in the biosynthetic pathways for branched-chain amino acids (leucine, valine and isoleucine). The B. phymatum ilvE mutant, KM60, was not auxotrophic for branched-chain amino acids and could grow well on minimal medium with pyruvate as carbon source and ammonia as nitrogen source. However, it grew poorer than the wild type strain when ammonia was substituted with valine or isoleucine as nitrogen source. The branched-chain amino acid aminotransferase activity of KM60 was significantly reduced relative to the WT strain, especially with isoleucine and valine as amino group donors. The C. taiwanensis leuC mutant, KM184-55, could not grow on a minimal medium with pyruvate as carbon source and ammonia as nitrogen source, but its growth was restored when leucine was added to the medium. Isopropylmalate isomerase activity of KM184-55 was completely lost compared to the WT strain. Both mutants recovered their respective enzyme activities after complementation with the wild-type ilvE or leuC genes, and were subsequently able to grow as well as their parental strains on minimal media. They were also able to form N-fixing nodules on M. pudica. We conclude that the biosynthesis of branched-chain amino acids is essential for the free-living growth of beta-rhizobia, as well as for their ability to form effective symbioses with their host plant.
Wen-Ming Chen; Jurgen Prell; Euan K James; Der-Shyan Sheu; Shih-Yi Sheu
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-5-3
Journal Detail:
Title:  Microbiology (Reading, England)     Volume:  -     ISSN:  1465-2080     ISO Abbreviation:  -     Publication Date:  2012 May 
Date Detail:
Created Date:  2012-5-4     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9430468     Medline TA:  Microbiology     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
National Kaohsiung Marine University, No. 142, Hai-Chuan Rd. Nan-Tzu, Kaohsiung City 811, Taiwan;
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