Article Abstract:
Extracellular nor intracellular products are not responsible for the aluminum tolerance of Rhizobium leguminosarum. This conclusion was based on experiments using strain UHM-5, a pSym- Exo- derivative of aluminum-tolerant R. leguminosarum bv. phaseoli strain CIAT899. It is known that bacterial extracellular polysaccharides (EPS) play a major role in preventing metal toxicity. However, the survival of UHM-5 in a medium containing high levels of aluminum, despite the lack of EPS, proves that it plays no role in the aluminum tolerance of R. leguminosarum.
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Article Abstract:
The ISRl2 insertion sequence (IS) of Rhizobium leguminosarum bv. viciae is 932 bp long and is 63-77% similar to the ISs of the Rhizobium and Sinorhizobium genera. ISRl2 has 17 bp terminal repeats and one open reading frame. The protein encoded by the open reading frame contains 290 residues and is basic in nature. The copy number of ISRl2 varies from one to eight. The greatest similarity in the copy number of homologous sequences is seen in S. fredii strains. The ISs homologous to ISRl2 are present on bacterial chromosome or plasmids.
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Article Abstract:
Ageneticcomplementation analysis of Rhizobium leguminosarum bv. phaseoli mutants defective in nodulation suppression was undertaken. The complemented mutants were characterized for nodulation and nitrogen fixation. The results suggested that the extent of the suppression response is the cumulative effect of the different stages of nodule development. Furthermore, nodulation suppression differs in various legumes, suggesting a complex machinery for plant response to invading rhizobia.
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