Characterization of a dszEABC operon providing fast growth on dibenzothiophene and construction of broad‐host‐range biodesulfurization catalysts

Abstract

A new operon for biodesulfurization (BDS) of dibenzothiophene and derivatives has been isolated from a metagenomic library made from oilcontaminated soil, by selecting growth of E. coli on DBT as the sulfur source. This operon is similar to a dszEABC operon also isolated by metagenomic functional screening but exhibited substantial differences: (i) the new fosmid provides much faster growth on DBT; (ii) associated dszEABC genes can be expressed without the need of heterologous expression from the vector promoter; and (iii) monooxygenases encoded in the fosmid cannot oxidize indole to produce indigo. We show how expression of the new dszEABC operon is regulated by the sulfur source, being induced under sulfurlimiting conditions. Its transcription is activated by DszR, a type IV activator οf σ N -dependent promoters. DszR is coded in a dszHR operon, whose transcription is in turn regulated by sulfur and presumably activated by the global regulator of sulfur metabolism CysB. Expression of dszH is essential for production of active DszR, although it is not involved in sulfur sensing or regulation. Two broad-host-range DBT biodesulfurization catalysts have been constructed and shown to provide DBT biodesulfurization capability to three Pseudomonas strains, displaying desirable characteristics for biocatalysts to be used in BDS processes.

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

“…However, it is also possible that regulation differs slightly from one genus (Gordonia) to another (Rhodococcus), given that regulatory sequences of the P dsz promoter regions are only partially conserved (10). Moreover, we cannot exclude the presence of additional regulators within the IGTS8 genome that could have dominant or synergistic effects on dsz operon regulation in vivo, such as the CymR homologue described in detail above, or the global CysB regulator (76). Taken together, several mechanistic details remain to be elucidated, offering valuable information on BDS regulation.…”

Interplay between Sulfur Assimilation and Biodesulfurization Activity in Rhodococcus qingshengii IGTS8: Insights into a Regulatory Role of the Reverse Transsulfuration Pathway

“…Moreover, we cannot exclude the possibility that other regulators are present within the IGTS8 genome and thus could have dominant or synergistic effects on dsz operon regulation in vivo . Some examples are the CymR homologue described in detail above and the global CysB regulator ( 79 ). Taken together, these results show that several mechanistic details remain to be elucidated, offering valuable information on biodesulfurization regulation.…”

Comparative Genomic Analysis of the Hydrocarbon-Oxidizing Dibenzothiophene-Desulfurizing Gordonia Strains

“…Condensed thiophenes may be responsible for most of the sulfur content in crude oil. Their presence results in lower oil quality and increased cost of processing; they also promote occurrence of acid rains and air contamination due to sulfur dioxide release from burning fuel [ 1 ]. Hydrodesulfurization processes, which are often used in oil refineries for sulfur removal, are economically inefficient.…”