Transcription factor OxyR regulates sulfane sulfur removal and L-cysteine biosynthesis in .

Sulfane sulfur, a collective term for hydrogen polysulfide and organic persulfide, often damages cells at high concentrations. Cells can regulate intracellular sulfane sulfur levels through specific mechanisms, but these mechanisms are unclear in . OxyR is a transcription factor capable of sensing oxidative stress and is also responsive to sulfane sulfur. In this study, we found that OxyR functioned directly in regulating sulfane sulfur in . OxyR binds to the promoter of and and regulates its expression, as revealed via electrophoretic mobility shift assay analysis, real-time quantitative PCR, and reporting systems. Overexpression of and reduced intracellular sulfane sulfur levels by over 30% and 20% in , respectively. RNA-sequencing analysis showed that the lack of OxyR downregulated the expression of sulfur assimilation pathway genes and/or sulfur transcription factors, which may reduce the rate of sulfur assimilation. In addition, OxyR also affected the biosynthesis of L-cysteine in . OxyR overexpression strain Cg-2 accumulated 183 mg/L of L-cysteine, increased by approximately 30% compared with the control (142 mg/L). In summary, OxyR not only regulated sulfane sulfur levels by controlling the expression of and in but also facilitated the sulfur assimilation and L-cysteine synthesis pathways, providing a potential target for constructing robust cell factories of sulfur-containing amino acids and their derivatives. IMPORTANCE is an important industrial microorganism used to produce various amino acids. In the production of sulfur-containing amino acids, cells inevitably accumulate a large amount of sulfane sulfur. However, few studies have focused on sulfane sulfur removal in . In this study, we not only revealed the regulatory mechanism of OxyR on intracellular sulfane sulfur removal but also explored the effects of OxyR on the sulfur assimilation and L-cysteine synthesis pathways in . This is the first study on the removal of sulfane sulfur in . These results contribute to the understanding of sulfur regulatory mechanisms and may aid in the future optimization of for biosynthesis of sulfur-containing amino acids.