Comparative characterization and functional genomic analysis of two Comamonas sp. strains for biodegradation of quinoline

Abstract BACKGROUND Quinoline is an ubiquitous pollutant widely spread in the environment, which can be eliminated efficiently by microbial degradation. In this study, two quinoline‐degrading Comamonas sp. strains Z1 and Z3 were isolated from activated sludge, and the degradation characteristics and genome annotation were investigated in detail. RESULTS Strain Z1 exhibited a superior capacity for quinoline degradation, which could completely degrade 50–300 mg L −1 quinoline within 8–24 h, whereas strain Z3 required 14–36 h to remove 50–200 mg L −1 quinoline. The suitable pHs for strains Z1 and Z3 were 8.0 and 7.0, respectively, and metal ions such as Mn 2+ , Ni 2+ , Cu 2+ , Co 2+ and Hg 2+ could greatly inhibit bacterial growth and quinoline degradation. Intermediates of 2‐hydroxyquinoline, 2,8‐dihydroxyquinoline, 8‐hydroxycoumarin, 2,3‐dihydroxyphenylpropionic acids and 2‐hydroxy‐6‐oxonona‐2,4‐diene‐1,9‐dioate were detected by liquid chromatography coupled to Q‐Exactive high‐resolution mass spectrometry. Thus, the biodegradation of quinoline by Comamonas sp. strains possibly proceeded via the 8‐hydroxycoumarin pathway. Genomic sequencing of strains Z1 and Z3 revealed a similar pattern, and a large number of functional genes were predicted to participate in degradation of aromatics. The key genes responsible for quinoline degradation also were identified, such as qor , mhp and bph . Furthermore, quinoline 2‐oxidoreductase (Qor) from strains Z1 and Z3 displayed 47.74%–61.17% similarities with previously reported Qor, which catalyzed the first step of quinoline degradation, and the maximal specific activity in cell‐free extracts of strains Z1 and Z3 was 0.264 and 0.062 U mg protein −1 , respectively. CONCLUSION This study should provide efficient microbial resources and useful genomic information for quinoline bioremediation. © 2020 Society of Chemical Industry