Chromium immobilization by extra- and intraradical fungal structures of arbuscular mycorrhizal symbioses
Language English Country Netherlands Media print-electronic
Document type Journal Article, Research Support, Non-U.S. Gov't
PubMed
27209517
DOI
10.1016/j.jhazmat.2016.05.017
PII: S0304-3894(16)30448-4
Knihovny.cz E-resources
- Keywords
- Arbuscular mycorrhizal fungi, Chromium, SEM-EDS, STXM, XAFS,
- MeSH
- Chromium analysis chemistry MeSH
- Phosphates metabolism MeSH
- Plant Roots metabolism microbiology MeSH
- Microscopy, Electron, Scanning MeSH
- Mycelium metabolism MeSH
- Mycorrhizae metabolism MeSH
- Surface Properties MeSH
- Plants metabolism MeSH
- Spectrometry, X-Ray Emission MeSH
- Fungal Structures * MeSH
- Symbiosis MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Names of Substances
- Chromium MeSH
- chromium hexavalent ion MeSH Browser
- Phosphates MeSH
Arbuscular mycorrhizal (AM) fungi can enhance plant Cr tolerance through immobilizing Cr in mycorrhizal roots. However, the detailed processes and mechanisms are unclear. The present study focused on cellular distribution and speciation of Cr in both extraradical mycelium (ERM) and mycorrhizal roots exposed to Cr(VI) by using field emission scanning electron microscopy equipped with energy dispersive X-ray spectrometer (FE-SEM-EDS), scanning transmission soft X-ray microscopy (STXM) and X-ray absorption fine structure (XAFS) spectroscopy techniques. We found that amounts of particles (possibly extracellular polymeric substances, EPS) were produced on the AM fungal surface upon Cr(VI) stress, which contributed greatly to Cr(VI) reduction and immobilization. With EDS of the surface of AM fungi exposed to various Cr(VI) levels, a positive correlation between Cr and P was revealed, suggesting that phosphate groups might act as counter ions of Cr(III), which was also confirmed by the XAFS analysis. Besides, STXM and XAFS analyses showed that Cr(VI) was reduced to Cr(III) in AM fungal structures (arbuscules, intraradical mycelium, etc.) and cell walls in mycorrhizal roots, and complexed possibly with carboxyl groups or histidine analogues. The present work provided evidence of Cr immobilization on fungal surface and in fungal structures in mycorrhizal roots at a cellular level, and thus unraveled the underlying mechanisms by which AM symbiosis immobilize Cr.
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