Characterization of the 3,4-Dichloroaniline Degradation Gene Cluster in Acinetobacter soli GFJ2

Abstract

3,4-Dichloroaniline (34DCA), a major metabolite of phenylurea herbicides, causes environmental contamination owing to its toxicity and recalcitrant properties. Acinetobacter soli strain GFJ2, isolated from soil potentially contaminated with herbicides, can degrade 34DCA. This study aimed to identify and characterize the 34DCA degradation gene cluster responsible for the conversion of 34DCA to 4,5-dichlorocatechol in the strain GFJ2. Genome analysis revealed one chromosome and seven plasmids in GFJ2, comprising 21, 75, and 3309 copies of rRNA, 75 tRNA, and protein-encoding genes, respectively. A gene cluster responsible for 34DCA degradation was identified, comprising dcdA, dcdB, and dcdC, which encode dioxygenase, flavin reductase, and aldehyde dehydrogenase, respectively. Transcriptional analysis indicated that this gene cluster is constructed as an operon, induced during 34DCA utilization. The heterologous expression of dcdA and dcdB in Escherichia coli confirmed their activity in degrading 34DCA to an intermediate metabolite, converted to 4,5-dichlorocatechol via a reaction involving the dcdC gene product, suggesting their involvement in 34DCA conversion to 4,5-dichlorocatechol. Deletion mutants of dcdA and dcdB lost 34DCA degradation ability, confirming their importance in 34DCA utilization in GFJ2. This study provides insights into the genetic mechanisms of 34DCA degradation by GFJ2, with potential applications in the bioremediation of environments contaminated by phenylurea herbicides.