# Enhanced Effect of Phytoextraction on Arsenic-Contaminated Soil by Microbial Reduction
## 4 Conclusions  
In this study, the functional iron-sulfur-reducing bacterial flora in soil was artificially enriched, which mainly consisted of Desulfovibrio, Escherichia-Shigella, Paraburholderia and Achromobater. The functional bacteria were used in the study of phytoremediation of arsenic-containing soil by _Pteris vittata_. Instead of destroying the structure of the soil microbial community, the inoculation of the bacterial solution showed good integration, which was mainly reflected in the increase in the relative abundance of Desulfovibrio.  
After a four-month phytoremediation period, the results revealed that the iron-sulfur-reducing bacteria effectively catalyzed the reductive dissolution of sulfate and iron oxides in the soil, promoting the transformation of arsenic in the reducible fraction to bioavailable arsenic. This transformation relied on the presence of organic matter to support the metabolic activities of the iron-sulfur-reducing bacteria. Consequently, the addition of straw-fermented organic fertilizer facilitated the above reactions and also provided essential nutrients for _Pteris vittata_, resulting in increased biomass.  
The metabolic activities of iron-sulfur-reducing bacteria and the small-molecule organic acids present in the organic fertilizers contributed to an increase in arsenite release. _Pteris vittata_ exhibited distinct uptake mechanisms for arsenate and arsenite, with arsenate being taken up through the phosphate system and competing with phosphates, while arsenite utilized an independent system. As a result, the accumulation and transport of  
Figure 10: Mechanism of phytoremediation of _Pteris vittata_ enhanced by bio-reduction.  
arsenic in _Pteris vittata_ were facilitated by the elevated concentrations of bioavailable arsenic and arsenite.  
Ultimately, with the assistance of iron-sulfur-reducing bacteria and organic fertilizers, the biomass of _Pteris vittata_ increased by 16.59%, and arsenic accumulation was elevated by 87.56%. Overall, the synergy between bio-reduction processes mediated by iron-sulfur-reducing bacteria and the specific uptake mechanisms of _Pteris vittata_ plays a crucial role in the efficient removal and remediation of arsenic from contaminated soil. These findings indicate that the utilization of iron-sulfur-reducing bacteria in assisting the phytoremediation of _Pteris vittata_ is a highly effective strategy with promising application prospects.  
Y.Z.: investigation, methodology, writing--original draft; J.C.: writing--reviewing, funding; P.C.: funding, investigation. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the National Key Research and Development Program (2019 YFC1803500); Science and Technology Innovation Program of Hunan Province: 2022 RC1039; the Natural Science Foundation of China (52004336, 52274287, 52074357); the Comprehensive Survey Project for Ecological Restoration in Dongting Lake Wetland: DD20230478; National 111 Project (No. B14034); and Natural Science Foundation of Hunan Province (2022 JJ30713).  
Not applicable.  
The datasets used in the current study are available on reasonable request.  
The authors declare that they have no known competing financial interest or personal relationships that could have appeared to influence the work reported in this paper.