Effects of a bacterial consortium from acid mine drainage on cadmium phytoextraction and indigenous soil microbial community

A major concern in developing microbially-assisted phytoextraction (MAP) is that the effects of introduced microbes on indigenous soil microbial community are profound and irreversible. To date, however, the microbial properties of soils subjected to MAP remain poorly understood. Therefore, we explored the effects of inoculation with a bacterial consortium enriched from acid mine drainage on not only the cadmium (Cd) phytoextraction efficiency of Averrhoa carambola but also the microbial properties of the Cd-contaminated soil. We conducted a field experiment and characterized the microbial community in the contaminated soil using next generation sequencing technology (Illumina MiSeq). The bacterial inoculation increased the Cd concentration in A. carambola shoot tissues by 20%-65%, leading to a relatively high Cd removal efficiency (4.63% annually). Meanwhile, there were no significant differences between the treatments in soil bacterial diversity and community composition one year after the initiation of the bacterial inoculation treatment. The most abundant genera of the introduced bacteria were found to either disappear from, or be present in similar relative abundance, in the soils of the different treatments, except Sulfobacillus. Collectively, our results provide evidence that MAP could be practiced with minor effects on indigenous soil microbial community.