Inoculation impact of seed-derived endophytic bacteria on growth promotion of metallophytes and their root microbiome composition in mine tailings

We have evaluated the impact of individual inoculations of eight phytostimulatory strains on the bacterial diversity in soil (bulk and rhizosphere soils) and roots of two metallicolous species (local ecotypes of Festuca arvernensis and Trifolium repens) grown in the greenhouse using a mixture of unsterilized heavy metal-contaminated soil (sourced from mine tailings, Zn 45,661, Pb 37,430, Cd 425, all ppm) with attapulgite (50:50 v/v) as a growth substrate. Illumina MiSeq technology (16S rDNA gene) applied on soil/root total DNA and inoculated strain genomic DNA was used to specify the inoculation impact on soil/root bacterial community and the survival of the inoculated strains.Seedlings were inoculated 3 months after sowing and harvested 2 months following inoculations. Inoculated bacteria belong to a strain collection assembled from surface-sterilized seeds of four metallophytes species, including F. arvernensis and T. repens. The four strains used to inoculate clover (2 Pantoea, 1 Herbiconiux, 1 Curtobacterium) differed from those used for fescue (1 Pseudomonas, 1 Dietzia, 1 Promicromonospora, 1 Streptomyces).