title: Lupinus albus plants acquire mercury tolerance when inoculated with an Hg-resistant Bradyrhizobium strain.
abstract: One strain of Bradyrhizobium canariense (L-7AH) was selected for its metal-resistance and ability to nodulate white lupin (Lupinus albus L.) plants, from a collection of rhizobial strains previously created from soils of the Almadén mining district (Spain) with varying levels of Hg contamination. Plants were inoculated with either strain L-7AH (Hg-tolerant) or L-3 (Hg-sensitive, used as control), and watered with nutrient solutions supplemented with various concentrations (0-200 μM) of HgCl2 in a growth chamber. L. albus inoculated with L-7AH were able to nodulate even at the highest concentration of Hg while those inoculated with L-3 had virtually no nodules at Hg concentrations above 25 μM. Plants inoculated with L-7AH, but not those with the control strain, were able to accumulate large amounts of Hg in their roots and nodules. Nodulation with L-7AH allowed plants to maintain constant levels of both chlorophylls and carotenoids in their leaves and a high photosynthetic efficiency, whereas in those inoculated with L-3 both pigment content and photosynthetic efficiency decreased significantly as Hg concentration increased. Nitrogenase activity of plants nodulated with L-7AH remained fairly constant at all concentrations of Hg used. Results suggest that this symbiotic pair may be used for rhizoremediation of Hg-contaminated soils.
authors.affiliation: Instituto de Ciencias Agrarias (ICA), CSIC, Serrano 115-bis, 28006 Madrid, Spain. Electronic address: ma.quinones@csic.es.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Quiñones
authors.forename: Beatriz
authors.initials: B
authors.lastname: Ruiz-Díez
authors.forename: Susana
authors.initials: S
authors.lastname: Fajardo
authors.forename: Miguel A
authors.initials: MA
authors.lastname: López-Berdonces
authors.forename: Pablo L
authors.initials: PL
authors.lastname: Higueras
authors.forename: Mercedes
authors.initials: M
authors.lastname: Fernández-Pascual
mesh_terms: D000222:Adaptation, Physiological; D001673:Biodegradation, Environmental; D020369:Bradyrhizobium / Q000145:classification / Q000502:physiology*; D002338:Carotenoids / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D031297:Lupinus / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology / Q000502:physiology*; D008628:Mercury / Q000378:metabolism*; D008906:Mining; D009591:Nitrogenase / Q000378:metabolism; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D055170:Plant Root Nodulation; D018517:Plant Roots / Q000378:metabolism; D053204:Root Nodules, Plant / Q000254:growth & development*; D012987:Soil; D012989:Soil Pollutants / Q000378:metabolism*; D013030:Spain; D013045:Species Specificity; D013312:Stress, Physiological; D013559:Symbiosis
chemical_list: D010940:Plant Proteins; D012987:Soil; D012989:Soil Pollutants; D002734:Chlorophyll; D002338:Carotenoids; D009591:Nitrogenase; D008628:Mercury
keywords: Bioremediation; Bradyrhizobium canariense; F(v)/F(m); Mercury; PGPR; Phytostabilization; ROS; Rhizoremediation; Symbiosis; VAZ; White lupin; plant-growth promoting rhizobacteria; reactive oxygen species; variable fluorescence/maximum fluorescence; violaxanthin + antheraxanthin + zeaxanthin