Isolation and characterization of nitrogen fixing heterotrophic bacteria from the rhizosphere of pioneer plants growing on mine tailings

► We isolated and characterized rhizospheric nitrogen-fixing bacteria. ► Most of the isolates were identified as Paenibacillus spp. ► P. durus had the highest nitrogenase activity, but was sensitive to heavy metals. ► Some strains maintained nitrogenase activity in high concentrations of Ni and Zn. ► Apparent redundancy in microbial functions in the rhizosphere probably helps to maintain processes in a range of environmental conditions.