Effects of plant growth-promoting bacteria isolated from copper tailings on plants in sterilized and non-sterilized tailings

• Ten strains of ACC-utilizing or N2-fixing bacteria were isolated and identified.
• The isolated PGPB strongly promoted the growth of plants on sterilized tailings.
• A consortium of 10 strains did not further increase the growth-promoting efficiency.
• Plant growth-promoting effects of the PGPB were weaker in non-sterilized tailings.

Ten strains of Cu-tolerant bacteria with potential plant growth-promoting ability were isolated by selecting strains with the ability to use 1-aminocyclopropane-1-carboxylate as a sole nitrogen source (designated ACC-B) or fix nitrogen (designated FLN-B) originating from the rhizosphere of plants growing on copper tailings. All 10 strains proved to have intrinsic ability to produce indole acetic acid and siderophores, and most of them could mobilize insoluble phosphate. In addition, a greenhouse study showed that ACC-B, FLN-B and a mixture of both had similar, potent ability to stimulate growth of Pennisetum purpureum, Medicago sativa and Oenothera erythrosepala plants grown on sterilized tailings. For instance, above-ground biomass of P. purpureum was 278–357% greater after 60 d growth on sterilized tailings in their presence. They could also significantly promote the growth of the plants grown on non-sterilized tailings, though the growth-promoting effects were much weaker. So, strategies for using of the plant growth-promoting bacteria in the practice of phytoremediation deserve further studies to get higher growth-promoting efficiency.