Identification of xenobiotic response element family transcription regulator SadR from sulfonamides-degrading strain Microbacterium sp. HA-8 and construction of biosensor to detect sulfonamides.

Deciphering the regulatory mechanisms of sulfonamides (SAs) metabolism will contribute to a deeper understanding of SAs degradation in the environment. In this study, a SAs-degrading strain Microbacterium sp. HA-8 harboring a highly conserved SAs-degrading genes sadABC was isolated. SadR was a newly discovered regulator, belonging to xenobiotic response element (XRE) family, which negatively regulated the transcription of sadAB genes. Specifically, SadR bound to the sadA promoter region to repress the expression of sadAB genes. While, SAs prevented SadR from binding to sadA promoter to induce the expression of sadAB genes. Then, a whole-cell biosensor, Escherichia coli DH5α/pSRmCherry was constructed to detect SAs. The dose-dependent fluorescence of the biosensor exhibited a good fit to Hill equation. In summary, this study revealed the regulatory mechanism of SAs degradation in strain HA-8 and developed an innovative biosensor technique for detecting SAs, holding promise for future applications in environmental monitoring.