Characterization of extrachromosomal replicons present in the extended host range Rhizobium sp. LPU83

TORRES TEJERIZO, G; DEL PAPA, M. F.; GIUSTI, M. A; DRAGHI, W. O.; LOZANO, M.; LAGARES, A.; PISTORIO, M.

PLASMID.

ACADEMIC PRESS INC ELSEVIER SCIENCE

Año: 2010 vol. 64 p. 177 - 185

0147-619X

In several rhizobia, bacteria that inhabit the soil in free-living conditions and associate in symbiosis with the root of legumes as nitrogen-fixing organisms, DNA plasmid can constitute a high percentage of the genome. We have characterized acid-tolerant isolates of rhizobia which have an extended host range to nodulate alfalfa, common bean, and Leucena leucocephala, represented by the Rhizobium sp. LPU83 strain. In this study we analyzed the plasmids of R. sp. LPU83 strain, in order to understand their role in the Medicago symbionts evolution and their involvement in symbiotic behavior. The pLPU83a plasmid was found to be transmissible and no phenotypic traits were associate with it. The symbiotic plasmid pLPU83b could transfer at very low frequencies under laboratory conditions only when pLPU83a was presented and could restore nodulation to a strain cured of its symbiotic plasmid, S. meliloti A818, but could not restore a full nitrogen fixation in association with alfalfa.