title: Mixed planting with a leguminous plant outperforms bacteria in promoting growth of a metal remediating plant through histidine synthesis.
abstract: The effectiveness of plant growth promoting bacteria (PGPB) in improving metal phytoremediation is still limited by stunted plant growth under high soil metal concentrations. Meanwhile, mixed planting with leguminous plants is known to improve yield in nutrient deficient soils but the use of a metal tolerant legume to enhance metal tolerance of a phytoremediator has not been explored. We compared the use of Pseudomonas brassicacearum, Rhizobium leguminosarum, and the metal tolerant leguminous plant Vicia sativa to promote the growth of Brassica juncea in soil contaminated with 400 mg Zn kg(-1), and used synchrotron based microfocus X-ray absorption spectroscopy to probe Zn speciation in plant roots. B. juncea grew better when planted with V. sativa than when inoculated with PGPB. By combining PGPB with mixed planting, B. juncea recovered full growth while also achieving soil remediation efficiency of >75%, the maximum ever demonstrated for B. juncea. μXANES analysis of V. sativa suggested possible root exudation of the Zn chelates histidine and cysteine were responsible for reducing Zn toxicity. We propose the exploration of a legume-assisted-phytoremediation system as a more effective alternative to PGPB for Zn bioremediation.
authors.affiliation: a School of GeoSciences, University of Edinburgh , Edinburgh , UK.
authors.forename: Gbotemi A
authors.initials: GA
authors.lastname: Adediran
authors.affiliation: a School of GeoSciences, University of Edinburgh , Edinburgh , UK.
authors.forename: Bryne T
authors.initials: BT
authors.lastname: Ngwenya
authors.affiliation: b Diamond Light Source, Harwell Science and Innovation Campus , Didcot , UK.
authors.forename: J Frederick W
authors.initials: JF
authors.lastname: Mosselmans
authors.affiliation: a School of GeoSciences, University of Edinburgh , Edinburgh , UK.
authors.forename: Kate V
authors.initials: KV
authors.lastname: Heal
authors.affiliation: a School of GeoSciences, University of Edinburgh , Edinburgh , UK.
authors.forename: Barbra A
authors.initials: BA
authors.lastname: Harvie
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D001673:Biodegradation, Environmental; D052918:Environmental Restoration and Remediation / Q000379:methods*; D006639:Histidine / Q000378:metabolism; D009149:Mustard Plant / Q000187:drug effects / Q000254:growth & development*; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development; D011549:Pseudomonas / Q000378:metabolism; D016961:Rhizobium leguminosarum / Q000378:metabolism; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*; D033022:Vicia sativa / Q000378:metabolism*; D056928:X-Ray Absorption Spectroscopy; D015032:Zinc / Q000378:metabolism*
chemical_list: D012989:Soil Pollutants; D006639:Histidine; D015032:Zinc
keywords: Zn bioremediation; leguminous plant; metal phytoremediation; plant growth promoting bacteria; μXANES analysis