Heterologous expression of sulfur: quinone oxidoreductase (Sqr) to improve Thioalkalivibrio versutus D301 desulfurization performance.

This article focuses on enhancing the biological desulfurization performance of the haloalkaliphilic sulfur-oxidizing bacterium *Thioalkalivibrio versutus* D301 through heterologous expression of the sulfide: quinone oxidoreductase (Sqr) gene from *Halomonas mongoliensis* JS01. The engineered strain, D301-sqr⁺, demonstrated improved sulfide oxidation rates and higher elemental sulfur yields—up to 95% at an oxidation-reduction potential (ORP) of −380 mV—compared to the wild-type strain. Transcriptome analysis revealed that expression of sqr altered sulfur metabolism gene regulation, notably downregulating the flavocytochrome c (fcc) and sox systems while upregulating genes involved in elemental sulfur oxidation. These findings suggest that metabolic engineering of sulfur-oxidizing bacteria like *T. versutus* D301 can effectively enhance desulfurization efficiency, offering potential benefits for industrial applications in environmental treatment.