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. J.; 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 insymbiosis with the root of legumes as nitrogen-fixing organisms, plasmid DNA can consti-tute a high percentage of the genome. We have characterized acid-tolerant isolates of rhi-zobia-here represented by the strain Rhizobium sp. LPU83-that have an extendednodulation-host range including alfalfa, the common bean, and Leucena leucocephala.Inthis study we analyzed the plasmids of R. sp. LPU83 in order to characterize their role inthe evolution of Medicago symbionts and their involvement in symbiotic behavior. ThepLPU83a plasmid was found to be transmissible with no associated phenotypic traits.The symbiotic plasmid pLPU83b could be transferred at very low frequencies under labo-ratory conditions only when pLPU83a was present; could restore nodulation to a straincured of its symbiotic plasmid, S. meliloti A818; but could not restore the full nitrogen fix-ation associated with alfalfa.