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Rhizospheric effect; Diazotrophic bacteria; Phaseolus vulgaris L.; Rhizobium; nifH; Terminal restriction fragment length; polymorphism; nifD; denaturing gradient gel; electrophoresis
Abstract:
The effect of common bean (Phaseolus vulgaris L.) on the composition of nitrogen fixing
bacterial assemblages in soil was studied by comparing planted and unplanted soil. The
community composition was studied by terminal restriction fragment length polymorphism
(T-RFLP) of the nitrogenase reductase gene (nifH ). Principal component analysis
(PCA) of T-RFLP profiles showed the separation of profiles from planted and unplanted soil.
Terminal restriction fragments (T-RFs) corresponding to rhizobial bacteria were identified
preferentially in planted soil; however most nifH T-RFs in soil could not be assigned to
T-RFs simulated from a database of known diazotrophs. To specifically study rhizobial
bacteria in the soil and nodules, PCR products from the alpha subunit of the nitrogenase
enzyme (nifD) were analyzed by denaturing gradient gel electrophoresis (DGGE). DGGE
results showed the specific stimulation of the rhizobial microsymbionts in planted soil.
