A novel antimony-selective ArsR transcriptional repressor and its specific detection of antimony trioxide in...

Extensively industrial applications and ever-accelerated anthropogenic activities have resulted in the dramatic accumulation of Sb₂O₃ contaminant in the environment, leading to adverse health effects on humans and ecosystems. Although arsenite has been subjected to numerous studies and ArsR-based whole-cell biosensors have been successfully applied in field testing of arsenite, there is limited information on the biological recognition element of Sb₂O₃ and its actual application in biosensor construction and environmental monitoring. In this study, we identified a specific recognition element of Sb₂O₃, SxArsR, in Sphingobium xenophagum C1 by the induced bioluminescent signal analysis of gene expression in response to Sb₂O₃ exposure. Compared to the other four groups of characterized ArsRs, the novel SxArsR lacks the third cysteine residue for binding of arsenite and has a conserved histidine-cysteine "HCXC" binding site that directly and specifically binds for Sb₂O₃. Sb₂O₃ can remove SxArsR from the core operator/promoter binding sequence in the -79 region upstream of the start codon of sxarsR. Based on the specificity of SxArsR protein and the sensitivity of SxArsR-binding DNA sequence, SxArsR-based whole-cell biosensor was constructed and showed a linear relationship (R² = 0.99) from 0.01 to 6.0 μM of Sb₂O₃ with a detection limit of 0.01 μM. The novel bacterial biosensor also exhibited a good performance in the detection of Sb₂O₃ in environmental water and sediment samples. Overall, SxArsR-based biosensor represents a promising strategy for Sb₂O₃ detection and may have a profound impact on further practical application of ArsR biosensor in the dual-signal simultaneous detection of arsenite and Sb₂O₃.