Elucidating the co-metabolism mechanism of 4-chlorophenol and 4-chloroaniline degradation by Rhodococcus through genomics and transcriptomics.

Co-metabolism is an effective strategy for the removal of refractory pollutants during biodegradation. This study reports that Rhodococcus DCB-5 can utilize 4-chlorophenol as a growth substrate to initiate the co-metabolic degradation of 4-chloroaniline. Comprehensive analyses of the genome, transcriptome, enzymes, and intermediate products identified key genes and a putative co-metabolic degradation pathway involved in the degradation process by Rhodococcus. Under optimal co-metabolic degradation conditions of pH 7 and 35°C, strain DCB-5 completely degraded 4-chlorophenol at an initial concentration of 50 mg/L, and achieved a 65.82% degradation rate for 4-chloroaniline at an initial concentration of 100 mg/L. Genome analysis indicated that the strain has the potential to degrade chlorinated aromatic compounds. The genes gpx, ygjG, ugpE, afuB, tfdB, catB, catA, and glnA were identified as core genes involved in the co-metabolic degradation process. Analysis of degradation intermediates revealed that 4-chlorophenol promotes the expression of the aniline dioxygenase-related gene glnA, facilitating the metabolism of 4-chloroaniline. A potential co-metabolic degradation pathway for strain DCB-5 is proposed. These findings may have implications for sites co-contaminated with chlorophenols and chloramines.