ISSN:
1573-5036
Keywords:
carbon metabolism
;
glutamate transport
;
mutants
;
Phaseolus vulgaris
;
symbiosis
;
Rhizobium sp.
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract Seven Tn5 induced mutants unable to use glutamate as sole carbon and nitrogen source were isolated from the effective Rhizobium leguminosarum bv. phaseoli strain P121-R. As indicated by restriction and hybridisation analysis, all the mutants arose from a single Tn5 insertion in the chromosome. The 14C-glutamate uptake rate of the mutants was 76 to 88% lower than that of strain P121-R. Inoculation of Phaseolus vulgaris cv. Labrador with these mutants significantly decreased shoot dry matter yield and the total nitrogen content respectively, as compared to inoculation with the parental strain P121-R. All the mutants formed nodules, however they were smaller, white to greenish and approximately 30% less numerous than those formed by strain P121-R. These observations suggest that glutamate transport and catabolism in R. leguminosarum bv. phaseoli P121-R may play an important role in the establishment of an effective symbiosis in field bean. None of the mutants isolated was an auxotroph. All mutants were unable to grow on aspartate suggesting that glutamate and aspartate, probably have the same transporter as indicated in Rhizobium meliloti and in Bacillus subtilis. All mutants readily used glutamine, proline, arginine as sole carbon and nitrogen source, but grew more slowly than the wild type strain. On the other hand, all the mutants were impaired in growth on histidine and γ-aminobutyrate as sole carbon and nitrogen source. As the catabolism of these amino acids occurs predominantly through glutamate, our results indicate that mutants are also impaired in their ability to use histidine and γ-aminobutyrate as a nitrogen source. Our results also suggest that other amino acids catabolized through the glutamate pathways may be an additional important carbon source for bacteroids in nodules.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00010994
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