ASSOCIATED BACTERIA INCREASE THE PHYTOEXTRACTION OF CADMIUM AND ZINC FROM A METAL-CONTAMINATED SOIL BY MYCORRHIZAL WILLOWS

Abstract

In order to enhance phytoremediation efficiency, we investigated the effects of dual inoculation with ectomycorrhizal fungi and the ectomycorrhiza associated bacteria Micrococcus luteus and Sphingomonas sp. on the growth and metal accumulation of willows (Salix viminalis x caprea) on contaminated soil. The bacterial strains were previously collected from sporocarps of ectomycorrhizal fungi. The bacteria increased plant growth and the mycorrhizal dependency of willows colonized with the ectomycorrhizal fungus Hebeloma crustuliniforme. The total cadmium (Cd) and zinc (Zn) accumulation in the shoot biomass was increased after inoculation with the fungal strain Hebeloma crustuliniforme in combination with Micrococcus luteus up to 53% and in combination with Sphingomonas sp. up to 62%, respectively. The dual inoculation in combination with Laccaria laccata did not increase the accumulation of Cd and Zn in the willows. We conclude that associated bacteria can enhance the ectomyorrhiza formation and growth of willows and, thereby, the Cd and Zn accumulation in the plant biomass. The results suggest that bacterial support of root growth promoting ectomycorrhizal fungi may be a promising approach to improve the remediation of metal-contaminated soils by using willows.