Biosynthesis of compatible solutes in rhizobial strains isolated from Phaseolus vulgaris nodules in Tunisian fields

BMC Microbiology

Research Article

Joaquín J Nieto¹  Mercedes Reina-Bueno¹  Montserrat Argandoña¹  Cristina Fernandez-Aunión¹  Carmen Vargas¹  Fernando Iglesias-Guerra²  Thouraya Ben Hamouda³  M Elarbi Aouani⁴ 

[1] Department of Microbiology and Parasitology, University of Seville, Spain;Department of Organic and Pharmaceutical Chemistry, University of Seville, Spain;Laboratory of Legumes. Centre of Biotechnology of Borj Cedria, BP 901, 2050, Hammam-lif, Tunisia;Laboratory of Legumes. Centre of Biotechnology of Borj Cedria, BP 901, 2050, Hammam-lif, Tunisia;NEPAD/North Africa Biosciences Network, National Research Center, El Buhouth St, 12311, Dokki, Cairo, Egypt;

关键词: Mannitol;    Trehalose;    Common Bean;    Compatible Solute;    Rhizobium Strain;   

DOI  :  10.1186/1471-2180-10-192

 received in 2010-04-24, accepted in 2010-07-16,  发布年份 2010

来源: Springer

【 摘 要 】

BackgroundAssociated with appropriate crop and soil management, inoculation of legumes with microbial biofertilizers can improve food legume yield and soil fertility and reduce pollution by inorganic fertilizers. Rhizospheric bacteria are subjected to osmotic stress imposed by drought and/or NaCl, two abiotic constraints frequently found in semi-arid lands. Osmostress response in bacteria involves the accumulation of small organic compounds called compatible solutes. Whereas most studies on rhizobial osmoadaptation have focussed on the model species Sinorhizobium meliloti, little is known on the osmoadaptive mechanisms used by native rhizobia, which are good sources of inoculants. In this work, we investigated the synthesis and accumulations of compatible solutes by four rhizobial strains isolated from root nodules of Phaseolus vulgaris in Tunisia, as well as by the reference strain Rhizobium tropici CIAT 899T.ResultsThe most NaCl-tolerant strain was A. tumefaciens 10c2, followed (in decreasing order) by R. tropici CIAT 899, R. leguminosarum bv. phaseoli 31c3, R. etli 12a3 and R. gallicum bv. phaseoli 8a3. 13C- and 1H-NMR analyses showed that all Rhizobium strains synthesized trehalose whereas A. tumefaciens 10c2 synthesized mannosucrose. Glutamate synthesis was also observed in R. tropici CIAT 899, R. leguminosarum bv. phaseoli 31c3 and A. tumefaciens 10c2. When added as a carbon source, mannitol was also accumulated by all strains. Accumulation of trehalose in R. tropici CIAT 899 and of mannosucrose in A. tumefaciens 10c2 was osmoregulated, suggesting their involvement in osmotolerance. The phylogenetic analysis of the otsA gene, encoding the trehalose-6-phosphate synthase, suggested the existence of lateral transfer events. In vivo13C labeling experiments together with genomic analysis led us to propose the uptake and conversion pathways of different carbon sources into trehalose. Collaterally, the β-1,2-cyclic glucan from R. tropici CIAT 899 was co-extracted with the cytoplasmic compatible solutes and its chemical structure was determined.ConclusionsThe soil bacteria analyzed in this work accumulated mainly disaccharides in response to NaCl stress. We could not find a direct correlation between the trehalose content of the rhizobial strains and their osmotolerance, suggesting that additional osmoadaptive mechanism should be operating in the most NaCl-tolerant strain R. tropici CIAT 899.

【 授权许可】

Unknown   
© Fernandez-Aunión et al; licensee BioMed Central Ltd. 2010. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.