Bacillus sp. is widely used in the remediation of uranium-contaminated sites. However, little is known about the competitive process of microbial community in the environment during bioremediation. The bioremediation of uranium tailings using Bacillus sp. was explored, and the bacterial community was analyzed by high-throughput sequencing at different stages of remediation. Bacillus sp. reduced the leaching of uranium from uranium tailings. The lowest uranium concentration was 17.25 μg/L. Alpha diversity revealed that the abundance and diversity of microorganisms increased with the extension of the culture time. The microbial abundance and diversity were higher in the treatment group than in the control group. The dominant species at the phyla level were Firmicutes and Proteobacteria in the uranium tailings environment, whereas the phylum of Proteobacteria was significantly increased in the treatment group. Based on the genus level, the proportions of Arthrobacter, Rhodococcus and Paenarthrobacter decreased significantly, whereas those of Clostridium sp., Bacillus and Pseudomonas increased dramatically. Hence, the remediation of uranium contamination in the environment was due to the functional microorganisms, which gradually became the dominant strain in the treatment, such as Desulfotomaculum, Desulfosporporosinus, Anaerocolumna, Ruminiclostridium and Burkholderia. These findings provided a promising outlook of the potential for remediation strategies of soil contaminated by uranium. The dynamic characteristics of the microbial community are likely to provide a foundation for the bioremediation process in practice.

Recent years have witnessed a steep rise in the use of SRB and IRB for the remediation of heavy metal contamination. This study investigated the effects of SRB and IRB on the physical and chemical properties of copper tailings. Besides, altered microbial community structure during the remediation process and the remediation mechanism were also explored. The results showed that bioremediation using SRB and IRB increased the pH of copper tailing and permeation time, and reduced ORP and the concentration of heavy metals, resulting in a friendly environment. The biological sealing was created from insoluble precipitates secreted by microbes in blocked seepage channels. This biological sealing prevented the infiltration of rain and oxygen and prevented the leaching of heavy metals. These findings have never been reported previously. In the exudates, the bioremediation resulted in the change of the dominant microorganisms from oxidised bacteria to SRB and IRB. In the copper mine tailings, the effect of bioremediation on microbial community varied with the depths of tailings. In addition, the species of microorganisms were also significantly different at different depths of tailings, and the key SRB, including Desulfosporosinus, Desulfotomaculum and Desulfovibrio, mainly existed in the middle and low part of mine tailings. GRAPHICAL ABSTRACT