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Abstract
Rhodococcus sp. P14 was isolated from crude-oil-contaminated sediments, and a wide range of polycyclic aromatic hydrocarbons (PAHs) could be used as the sole source of carbon and energy. A key CYP450 gene, designated as cyp108j1 and involved in the degradation of PAHs, was identified and was able to hydroxylate various PAHs. However, the regulatory mechanism of the expression of cyp108j1 remains unknown. In this study, we found that the expression of cyp108j1 is negatively regulated by a LuxR (helix-turn-helix transcription factors in acyl-homoserine lactones-mediated quorum sensing) family regulator, NarL (nitrate-dependent two-component regulatory factor), which is located upstream of cyp108j1. Further analysis revealed that NarL can directly bind to the promoter region of cyp108j1. Mutational experiments demonstrated that the binding site between NarL and the cyp108j1 promoter was the palindromic sequence GAAAGTTG-CAACTTTC. Together, the finding reveal that NarL is a novel repressor for the expression of cyp108j1 during PAHs degradation.
Highlights
As natural environmental products, polycyclic aromatic hydrocarbons (PAHs) have been present on the earth for many years [1]
The physical and chemical properties of PAHs mean they do not degrade in the environment, existing ubiquitously in the air, soil, and water [3]. These PAHs can bioaccumulate through food chains, which poses a potential hazard to human health [4,5,6,7]
In the last few decades, research on microbial degradation of PAHs has advanced significantly and a number of PAH-degrading isolates have been reported [1,11,12,13], with some of the isolates belonging to the Rhodococcus genus
Summary
Polycyclic aromatic hydrocarbons (PAHs) have been present on the earth for many years [1]. GAAAGTTG was mutated to TCCCTGGT (Figure 6C), no shift band was observed (Figure 6B), which proved that the palindrome sequence was necessary for the binding between NarL and P3-B. Taking these results together, NarL, as a repressor, can bind to the palindromic sequences (GAAAGTTG-CAACTTTC) upstream of cyp108j1, resulting in lower expression of cyp108j1. If the palindrome sequence GAAAGTTG was mutated to TCCCTGGT (Figure 6C), no shift band was observed (Figure 6B), which proved that the palindrome sequence was necessary for the binding between NarL and P3-B Taking these results together, NarL, as a repressor, can bind to the palindromic sIenqt.uJ.eMnocle. NarL, as a repressor, can bind to the palindromic sIenqt.uJ.eMnocle. sSci(.G20A20A, 2A1,G98T3TG-CAACTTTC) upstream of cyp108j1, resulting in lower expression ofo1f1 cyp108j1
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