The interplay between sulfur assimilation and biodesulfurization phenotype in Rhodococcus qingshengii IGTS8: Insights into a regulatory role of the reverse transsulfuration pathway

Biodesulfurization (BDS) is a process that selectively removes sulfur from dibenzothiophene and its derivatives. Several mesophilic natural biocatalysts have been isolated, harboring the highly conserved desulfurization operon dszABC. Even though the desulfurization phenotype is known to be significantly repressed by methionine, cysteine, and inorganic sulfate, the available information on the metabolic regulation of gene expression is still limited. In this study, scarless knockouts of the sulfur metabolism-related cbs and metB genes are constructed in the desulfurizing strain Rhodococcus sp. IGTS8. We provide sequence analyses for both enzymes of the reverse transsulfuration pathway and report their involvement in the sulfate- and methionine-dependent repression of the biodesulfurization phenotype, based on desulfurization assays in the presence of different sulfur sources. Additionally, the positive effect of cbs and metB gene deletions on dsz gene expression in the presence of both sulfate and methionine, but not cysteine, is uncovered and highlighted.