title: Transformation and Immobilization of Chromium by Arbuscular Mycorrhizal Fungi as Revealed by SEM-EDS, TEM-EDS, and XAFS.
abstract: Arbuscular mycorrhizal fungi (AMF), ubiquitous soil fungi that form symbiotic relationships with the majority of terrestrial plants, are known to play an important role in plant tolerance to chromium (Cr) contamination. However, the underlying mechanisms, especially the direct influences of AMF on the translocation and transformation of Cr in the soil-plant continuum, are still unresolved. In a two-compartment root-organ cultivation system, the extraradical mycelium (ERM) of mycorrhizal roots was treated with 0.05 mmol L(-1) Cr(VI) for 12 days to investigate the uptake, translocation, and transformation of Cr(VI) by AMF using inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy equipped with energy-dispersive spectroscopy (SEM-EDS), transmission electron microscopy equipped with energy-dispersive spectroscopy (TEM-EDS), and X-ray-absorption fine structure (XAFS) technologies. The results indicated that AMF can immobilize quantities of Cr via reduction of Cr(VI) to Cr(III), forming Cr(III)-phosphate analogues, likely on the fungal surface. Besides this, we also confirmed that the extraradical mycelium (ERM) can actively take up Cr [either in the form of Cr(VI) or Cr(III)] and transport Cr [potentially in the form of Cr(III)-histidine analogues] to mycorrhizal roots but immobilize most of the Cr(III) in the fungal structures. Based on an X-ray absorption near-edge spectroscopy analysis of Cr(VI)-treated roots, we proposed that the intraradical fungal structures can also immobilize Cr within mycorrhizal roots. Our findings confirmed the immobilization of Cr by AMF, which plays an essential role in the Cr(VI) tolerance of AM symbioses.
authors.affiliation: University of Chinese Academy of Sciences , Beijing 100049, People's Republic of China.
authors.forename: Songlin
authors.initials: S
authors.lastname: Wu
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.affiliation: University of Chinese Academy of Sciences , Beijing 100049, People's Republic of China.
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Sun
authors.affiliation: University of Chinese Academy of Sciences , Beijing 100049, People's Republic of China.
authors.forename: Zhaoxiang
authors.initials: Z
authors.lastname: Wu
authors.forename: Tao
authors.initials: T
authors.lastname: Li
authors.affiliation: Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences , Changsha 410125, People's Republic of China.
authors.forename: Yajun
authors.initials: Y
authors.lastname: Hu
authors.affiliation: University of Chinese Academy of Sciences , Beijing 100049, People's Republic of China.
authors.forename: Dan
authors.initials: D
authors.lastname: Su
authors.forename: Jitao
authors.initials: J
authors.lastname: Lv
authors.forename: Gang
authors.initials: G
authors.lastname: Li
authors.forename: Zhensong
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences , Beijing 100049, People's Republic of China.
authors.forename: Lirong
authors.initials: L
authors.lastname: Zheng
authors.affiliation: Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences , Beijing 100049, People's Republic of China.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Baodong
authors.initials: B
authors.lastname: Chen
mesh_terms: D002857:Chromium / Q000032:analysis / Q000378:metabolism / Q000493:pharmacokinetics*; D018552:Daucus carota / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology; D006639:Histidine / Q000737:chemistry / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D025282:Mycelium / Q000378:metabolism; D038821:Mycorrhizae / Q000187:drug effects / Q000502:physiology*; D010710:Phosphates / Q000737:chemistry; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology*; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism / Q000493:pharmacokinetics*; D013052:Spectrometry, X-Ray Emission; D013559:Symbiosis; D056928:X-Ray Absorption Spectroscopy / Q000379:methods
chemical_list: D010710:Phosphates; D012987:Soil; D012989:Soil Pollutants; D002857:Chromium; D006639:Histidine