LuxR solo regulates recalcitrant aromatic compound biodegradation: Repression and activation of dibenzofuran-catabolic genes expression in a Rhodococcus sp.

Aromatic compounds contribute to the category of prevalent, toxic, and persistent pollutants in the environment. Microbial degradation of aromatic pollutants is eco-friendly, which depends on efficient manipulation of catabolic enzyme activity. As homologs of quorum sensing LuxR family regulators, LuxR solos play important roles in cell-cell interaction; however, there are few studies on its regulation of recalcitrant aromatic compounds degradation. In this study, the transcriptional regulatory mechanism of dibenzofuran catabolic genes controlled by LuxR solo was elucidated in the dioxin-degrader Rhodococcus sp. strain p52. LuxR solo encoded by catabolic plasmid pDF01 was detected to bind to the promoters of dfdA and dfdB and inhibit the genes expression, which are involved in dibenzofuran degradation. The repression of the LuxR on the catabolic genes expression was not affected by dibenzofuran, but could be alleviated by the intermediate of dibenzofuran degradation, salicylic acid. RNA-Seq analysis suggested that the LuxR solo related to regulating the expression of multiple key genes on the chromosome and catabolic plasmids pDF02. Phylogenetic analysis indicated that LuxR solos frequently distribute among aromatics-degrading bacteria. This study reveals the molecular regulatory network of dibenzofuran degradation mediated by LuxR solo and deepens the understanding of transcriptional regulatory mechanisms of aromatic compounds degradation.