The Two-Component System RsrS-RsrR Regulates the Tetrathionate Intermediate Pathway for Thiosulfate Oxidation in .

() is a common bioleaching bacterium that possesses a sophisticated and highly efficient inorganic sulfur compound metabolism network. Thiosulfate, a central intermediate in the sulfur metabolism network of and other sulfur-oxidizing microorganisms, can be metabolized via the tetrathionate intermediate (SI) pathway catalyzed by thiosulfate:quinol oxidoreductase (Tqo or DoxDA) and tetrathionate hydrolase (TetH). In , there is an additional two-component system called RsrS-RsrR. Since and are arranged as an operon with and in the genome, we suggest that the regulation of the SI pathway may occur via the RsrS-RsrR system. To examine the regulatory role of the two-component system RsrS-RsrR on the SI pathway, Δ and Δ strains were constructed in using a newly developed markerless gene knockout method. Transcriptional analysis of the cluster in the wild type and mutant strains revealed positive regulation of the SI pathway by the RsrS-RsrR system. A 19 bp inverted repeat sequence (IRS, AACACCTGTTACACCTGTT) located upstream of the promoter was identified as the binding site for RsrR by using electrophoretic mobility shift assays (EMSAs) and promoter-probe vectors . In addition, Δ, and Δ strains cultivated in KSO-medium exhibited significant growth differences when compared with the wild type. Transcriptional analysis indicated that the absence of or had different effects on the expression of genes involved in sulfur metabolism and signaling systems. Finally, a model of tetrathionate sensing by RsrS, signal transduction via RsrR, and transcriptional activation of - was proposed to provide insights toward the understanding of sulfur metabolism in . This study also provided a powerful genetic tool for studies in .