title: The hyperaccumulator Sedum plumbizincicola harbors metal-resistant endophytic bacteria that improve its phytoextraction capacity in multi-metal contaminated soil.
abstract: Endophyte-assisted phytoremediation has recently been suggested as a successful approach for ecological restoration of metal contaminated soils, however little information is available on the influence of endophytic bacteria on the phytoextraction capacity of metal hyperaccumulating plants in multi-metal polluted soils. The aims of our study were to isolate and characterize metal-resistant and 1-aminocyclopropane-1-carboxylate (ACC) utilizing endophytic bacteria from tissues of the newly discovered Zn/Cd hyperaccumulator Sedum plumbizincicola and to examine if these endophytic bacterial strains could improve the efficiency of phytoextraction of multi-metal contaminated soils. Among a collection of 42 metal resistant bacterial strains isolated from the tissues of S. plumbizincicola grown on Pb/Zn mine tailings, five plant growth promoting endophytic bacterial strains (PGPE) were selected due to their ability to promote plant growth and to utilize ACC as the sole nitrogen source. The five isolates were identified as Bacillus pumilus E2S2, Bacillus sp. E1S2, Bacillus sp. E4S1, Achromobacter sp. E4L5 and Stenotrophomonas sp. E1L and subsequent testing revealed that they all exhibited traits associated with plant growth promotion, such as production of indole-3-acetic acid and siderophores and solubilization of phosphorus. These five strains showed high resistance to heavy metals (Cd, Zn and Pb) and various antibiotics. Further, inoculation of these ACC utilizing strains significantly increased the concentrations of water extractable Cd and Zn in soil. Moreover, a pot experiment was conducted to elucidate the effects of inoculating metal-resistant ACC utilizing strains on the growth of S. plumbizincicola and its uptake of Cd, Zn and Pb in multi-metal contaminated soils. Out of the five strains, B. pumilus E2S2 significantly increased root (146%) and shoot (17%) length, fresh (37%) and dry biomass (32%) of S. plumbizincicola as well as plant Cd uptake (43%), whereas Bacillus sp. E1S2 significantly enhanced the accumulation of Zn (18%) in plants compared with non-inoculated controls. The inoculated strains also showed high levels of colonization in rhizosphere and plant tissues. Results demonstrate the potential to improve phytoextraction of soils contaminated with multiple heavy metals by inoculating metal hyperaccumulating plants with their own selected functional endophytic bacterial strains.
authors: Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal; Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China. Electronic address: cathymaying@gmail.com.
authors: Ying
authors: Y
authors: Ma
authors: Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal; CBQF - Centro de Biotecnologia e Química Fina - Laboratório Associado, Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Arquiteto Lobão Vital, Apartado 2511, 4202-401 Porto, Portugal; Research Centre on Health and Environment, School of Allied Health Sciences, Polytechnic Institute of Porto, Rua Valente Perfeito, 322, 4400-330 Vila Nova de Gaia, Portugal.
authors: Rui S
authors: RS
authors: Oliveira
authors: Soil Science Agricultural College, Guizhou University, Guiyang 550025, China.
authors: Fengjiao
authors: F
authors: Nai
authors: Department of Life Sciences, Central University of Tamil Nadu, Collectorate Annexe, Thanjavur Road, Thiruvarur 610 004, Tamil Nadu, India.
authors: Mani
authors: M
authors: Rajkumar
authors: Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, Shandong 264003, China.
authors: Yongming
authors: Y
authors: Luo
authors: Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal.
authors: Inês
authors: I
authors: Rocha
authors: Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal.
authors: Helena
authors: H
authors: Freitas
mesh_terms: D001407:Bacillus / Q000302:isolation & purification / Q000378:metabolism; D001673:Biodegradation, Environmental; D018533:Biomass; D002104:Cadmium / Q000493:pharmacokinetics; D060026:Endophytes / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism; D019216:Metals, Heavy / Q000032:analysis / Q000378:metabolism* / Q000494:pharmacology; D018517:Plant Roots / Q000382:microbiology; D058441:Rhizosphere; D031963:Sedum / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology*; D012987:Soil; D012989:Soil Pollutants / Q000032:analysis / Q000493:pharmacokinetics*; D015032:Zinc / Q000493:pharmacokinetics
chemical_list: D007210:Indoleacetic Acids; D019216:Metals, Heavy; D012987:Soil; D012989:Soil Pollutants; D002104:Cadmium; C030737:indoleacetic acid; D015032:Zinc
keywords: Endophytic bacteria; Heavy metals; Hyperaccumulator; Phytoextraction; Sedum plumbizincicola