污染分枝杆菌DM32对吲哚的生物降解：过程特征及IifR介导的分子机制

Abstract

Isolated Burkholderia contaminans DM32 degrades indole in diverse environments. • DM32 fully degrades indole in livestock manure wastewater within 24 h. • IifR regulator activates indole degradation via CGGATA motif binding in iif promoter. • IifC / iifD genes essential for indole degradation and indigo biosynthesis in DM32. • DM32 shows dual potential for bioremediation. Indole is a recalcitrant N -heterocyclic pollutant released from livestock and industrial waste, posing serious ecological and toxicological hazards. Despite numerous reported indole-degrading bacteria, the molecular regulatory circuits of indole catabolism within Burkholderia remain poorly resolved. In this study, a novel indole-degrading bacterium, Burkholderia contaminans DM32, was isolated from contaminated production water. Strain DM32 exhibited robust indole-removal capacity across broad environmental ranges with optimal degradation performance at 30 °C and pH 5.0-7.0, accompanied by indigo formation as a metabolic by-product. Notably, DM32 achieved complete indole removal from livestock manure wastewater within 24 h, demonstrating its feasibility for pollutant remediation in complex real-world matrices. Genomic and functional assays revealed that indole-induced flavoproteins IifCD are indispensable for both indole degradation and indigo biosynthesis. Transcriptomic profiling implies the existence of auxiliary oxidative pathways that may functionally compensate for loss of the canonical iif -driven catabolism. Furthermore, we identified the AraC/XylS-family transcriptional regulator IifR as a key positive regulator of the iif gene cluster. Mechanistically, indole acts as an effector molecule to trigger iifR expression, and the resulting IifR protein specifically recognizes and binds the palindromic CGGATA motif (−236 to −258) within the iif promoter via its C-terminal domain, thereby activating transcription of the downstream iif gene cluster, while the N-terminal domain