Open AccessEffect of a Sinorhizobium meliloti Strain with a Modified putA Gene on the Rhizosphere Microbial Community of Alfalfa
Author(s) -
Pieter van Dillewijn,
Pablo J. Villadas,
Nicolás Toro
Publication year - 2002
Publication title -
applied and environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.552
H-Index - 324
eISSN - 1070-6291
pISSN - 0099-2240
DOI - 10.1128/aem.68.9.4201-4208.2002
Subject(s) - rhizosphere , sinorhizobium meliloti , microbial inoculant , biology , strain (injury) , inoculation , microbial population biology , rhizobiaceae , plasmid , 16s ribosomal rna , sinorhizobium , terminal restriction fragment length polymorphism , bacteria , microbiology and biotechnology , botany , gene , symbiosis , horticulture , restriction fragment length polymorphism , polymerase chain reaction , genetics , anatomy
The success of a rhizobial inoculant in the soil depends to a large extent on its capacity to compete against indigenous strains. M403, a Sinorhizobium meliloti strain with enhanced competitiveness for nodule occupancy, was recently constructed by introducing a plasmid containing an extra copy of a modified putA (proline dehydrogenase) gene. This strain and M401, a control strain carrying the same plasmid without the modified gene, were used as soil inoculants for alfalfa in a contained field release experiment at León, Spain. In this study, we determined the effects of these two strains on the indigenous microbial community. 16S rRNA genes were obtained from the rhizosphere of alfalfa inoculated with strain M403 or strain M401 or from noninoculated plants by amplification of DNA from soil with bacterial group-specific primers. These genes were analyzed and compared by restriction fragment length polymorphism and temperature gradient gel electrophoresis. The results allowed us to differentiate between alterations in the microbial community apparently caused by inoculation and by the rhizosphere effect and seasonal fluctuations induced by the alfalfa plants and by the environment. Only moderate inoculation-dependent effects could be detected, while the alfalfa plants appeared to have a much stronger influence on the microbial community.