Use of
Rhizobium-Legume symbiosis in bioremediation of polluted soils
C.I.F.A. Las Torres-Tomejil, Alcalá del
Río, 41200-Sevilla [cifatorr@cap.junta-andalucia.es] and Department of
Microbiology and Pathology, University of Sevilla, 41020-Sevilla. SPAIN
[palomares@us.es]
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The symbiosis of legumes with Rhizobium has been extensively studied given de
ability of this plant-bacteria interaction to use atmospheric nitrogen. Legumes
have been also used in regeneration of soils. Our groups are currently involved
in a project aimed to evaluate the possibilities of the symbiosis legume-Rhizobium in bioremediation of soils polluted by
heavy metals, namely copper, lead and also arsenic. We have isolated Rhizobia from contaminated soils from the
Aznalcóllar mine area, some of them being resistant to relatively high
concentrations of these elements (up to 500 ppm). The presence of the
corresponding resistance operons in some of the strains has been revealed by
PCR and Southern hybridisation with heterologous probes. With regard to plants,
we have used five different genera of legumes collected from contaminated areas (Lotus,
Medicago, Trifolium, Vicia and
Lupinus) and we are currently
analysing their capability of accumulation of toxic elements in plant tissues.
Besides, nodulation and nitrogen fixation studies have been carried out using
these native rhizobia
and their host plants both in contaminated and non-contaminated soils in an
attempt to use native germplasm in bioremediation of soils (legumeremediation).
(Project supported by Ministerio de Ciencia y
Tecnología, INIA TRA02- 015-C2).