Microbial Degradation of 3-Chloroanilne by two Bacterial Strains isolated from Common Effluent Treatment Plant

Abstract

The diversity has been examined of the plasmids and of the gene tdnQ, involved in oxidative deamination of aniline in three bacterial isolates that are able to metabolise both aniline and 3-chloroaniline (3-CA). Strains A and B were isolated in this study from a wastewater treatment plant and were identified as Comamonas testosterone and Delftia acidovorans, respectively. Strain C, identified as Delftia acidovorans, was isolated from a linuron-treated soil. Both Delftia and Comamonas belong to the family of the Comamonadaceae. All three strains possess a large plasmid of ca. 100 kb, but the plasmids from only 4 strains could be transferred to a recipient strain by selecting on aniline or 3-CA as sole source of carbon and/or nitrogen. Plasmid transfer experiments and Southern hybridization revealed that the plasmid of strain A encodes total aniline but not 3-CA degradation, while the plasmids of strains C and B were only responsible for the oxidative deamination of aniline. Using specific primers for the tdnQ gene, from Pseudomonas putida, the diversity of the PCR amplified fragments in the five strains was examined by denaturing gradient gel electrophoresis (DGGE). With DGGE, three different clusters of the tdnQ fragment could be distinguished. Sequencing data showed that the tdnQ sequences of A, C, B were very closely related, while the tdnQ fragment of BN3.1 and P. putida were only about 83% identical to the other sequences. Northern hybridization revealed that the tdnQ gene is only transcribed in the presence of aniline and not when only 3-CA is present.