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The soil ecosystem is easily polluted by heavy metals. Cadmium (Cd) and lead (Pb), as the main pollutants of heavy metals, cause much harm to the soil ecosystem. However, the impact of the two chemicals on rhizosphere microorganisms remains almost unknown. The change of catalase (CAT) activity was consistent with the microbial biomass. 16S rRNA gene sequencing was performed on soil samples to study the toxic effect of heavy metals. On performing sequence analysis at the phylum and family taxonomic levels, 32 identified phyla and 303 families were observed. The dominant phylum was Proteobacteria followed by Bacteroidetes, Acidobacteria, and Actinobacteria. The relative abundance of the dominant phyla was obviously changed under the stress of Cd and Pb, suggesting that the heavy metal input had affected the microbial community structure. At the Order and Family levels, there was different variation of richness and diversity in Cd and Pb group as compared to those in the control group. Furthermore, abundance and similarity analysis showed the differences between Cd and Pb, indicating different toxicology effect on rhizosphere microbial communities because of the unique properties. This study provided a novel insight into the composition of microbial communities of rhizosphere, which could be used to evaluate the soil environment.

Mucor circinelloides, selected from mine tailings for heavy metal bioremediation, was characterized at the genetic level by internal transcribed spacer (ITS) analysis. M. circinelloideswas first applied for the absorption of heavy metals {Fe(iii), Mn(ii), Cu(ii), Zn(ii), and Pb(ii)}. The minimal inhibitory concentration test showed that M. circinelloidescould tolerate relatively high concentrations of heavy metals. M. circinelloidescould uptake 79.5%, 44.1%, 62.5%, 56.5%, and 85.5% of Fe(iii), Mn(ii), Cu(ii), Zn(ii), and Pb(ii), respectively, from the initial concentration of 20 mg L−1under optimum conditions (pH 8; 30 °C). Monitoring the change in ATPase activity at certain intervals indicated that the mechanism of bioremediation was directly related to the energy consumption. M. circinelloideswill be widely used for in-situremediation in special environment because of strong vitality and excellent bioremediation efficiency.