Copper sorption and accumulation by the extraradical mycelium of different Glomus spp. (arbuscular mycorrhizal fungi) isolated from the same polluted soil

Abstract

The form and localisation of Cu accumulation in the extraradical mycelium (ERM) of three arbuscular mycorrhizal fungi (AMF), isolated from the same polluted soil contaminated with the Cu and Arsenate, was studied. There were differences in the capacity of the ERM of the three AMF to sorb and accumulate Cu. Glomus caledonium BEG133 had a significantly lower Cu-sorption capacity than Glomus mosseae BEG132 and Glomus claroideum BEG134 isolated from the polluted soil as well as an isolate of G. mosseae BEG25 from a non-polluted soil. This was directly related to the cation exchange capacity (CEC) of the ERM of these fungi. Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) linked to an energy dispersive X-ray spectrometer (EDAX) gave more detailed information, showing that the ERM of AMF from the polluted soil was able to accumulate Cu in the mucilaginous outer hyphal wall zone, cell wall and inside the hyphal cytoplasm. The EDAX spectra showed that the accumulated Cu was mainly associated with Fe in the mucilaginous outer hyphal wall zone and in the cell wall. Cu was associated with traces of arsenate inside the cytoplasm of the ERM of Glomus mosseae BEG132 but this was not visible inside the ERM of Glomus caledonium BEG133 or Glomus claroideum BEG134. This work suggests that the ERM of AMF is able to sorb and accumulate Cu, but different tolerance mechanisms exist between the three AMF isolated from the same polluted soil providing further evidence for functional diversity within populations of AMF in soils.