Aniline Degradation via 2-Aminophenol: Genetic Basis, Broadened Players and Interspecies Cooperation

For more than four decades, the catechol route has been the only genetically resolved aerobic pathway for aniline biodegradation. The genetic basis of aniline degradation via 2-aminophenol is relatively unexplored. In this study, Pseudomonas sp. ANNB1 degraded aniline aerobically with trace accumulation of 2-aminophenol, phenylhydroxylamine, nitrosobenzene and nitrobenzene. The ANNB1 genome encodes a dmp gene cluster and two nbz operons, consistent with the degradation ability of this strain towards phenol and 2-aminophenol. During aniline degradation, the transcription levels of both dmp and nbz genes were significantly elevated. Deletion of nbzCaCb caused 2-aminophenol accumulation and a 79.5% reduction in aniline removal, whereas loss of dmpMNOP abolished aniline degradation. Compared to previously characterised aniline-degradative gene clusters, the dmp operon has a broader phylogenetic distribution. Moreover, co-cultures of phenol- and 2-aminophenol-degraders showed synergistic aniline degradation in the presence of additional carbon and nitrogen sources. In conclusion, phenol hydroxylase can initiate aniline degradation by catalysing it to 2-aminophenol. Furthermore, this work provides a genetic framework for engineering synthetic consortia targeting multiple pollutants.