Change of microbial communities in heavy metals-contaminated rhizosphere soil with ectomycorrhizal fungi Suillus luteus inoculation

Ectomycorrhizal fungus Suillus luteus has been recognized to harbor the ability of improving rhizosphere soil nutrients and absorbing heavy metals (HMs), but effects of S. luteus inoculation on microbial communities in HM-contaminated rhizosphere soil remain unclear. A comprehensive study involving physicochemical analysis and comparative metagenomics was employed to determine the differences in soil properties, structure and function of microbial communities between inoculation and non-inoculation groups. Results showed that the concentrations of soil organic carbon, total carbon, and total nitrogen of rhizosphere soil in inoculation group were 2.1, 1.7, and 1.3 times as high as that in uninoculated group. Besides, concentrations of Cd, Pb, As, Cu, and Zn in inoculation soil were 79 %, 33 %, 65 %, 14 %, and 51 % lower than that in uninoculated soil. Metagenomic study indicated that S. luteus inoculation had no strong effect on diversity and richness of microbial communities in rhizosphere soil, but increased the relative abundance of certain HM-resistant microorganisms such as phylum Actinobacteria and genus Streptomyces. Metabolism-oriented functional annotation further revealed that in inoculation group the abundance of coding sequences related to nutrients metabolism (e.g., carbon, nitrogen, and sulfur metabolism) and HMs resistance (e.g., HMs transformation and efflux) distinctly differed from that in uninoculated group. In short, our findings may elucidate the potential contribution of S. luteus inoculation that affects the structure composition and metabolic functions of microbial communities to mediate the concentration variation of nutrients and HMs in rhizosphere ecosystem.