Microbial degradation of 4-chloroaniline by a bacterial consortium

In this study, we have isolated four different species from effluent contaminated soil using a mixture of aniline and 4-chloroaniline (4CA) as principal carbon sources. The four species were identified as Pseudomonas stutzeri A, Comamonas testosterone B, Pseudomonas putida C and Stenotrophomonas maltophilia D. Growth studies on aniline and 4CA as single and mixed substrates demonstrated that the bacteria preferred to grow on and utilize aniline rather than 4CA. However, despite 100% disappearance of the parent substrates, the degradation of 4CA was always characterized by incomplete dechlorination and 4-chlorocatechol accumulation. HPLC-UV analysis showed that 4-chlorocatechol was further degraded via an ortho-cleavage pathway by the bacterial consortium. This hypothesis was supported by the results from enzyme assays of the crude cell extract of the consortium revealing catechol 1,2-dioxygenase activity which converted catechol and 4-chlorocatechol to cis,cis-muconic acid and 3-chloro-cis,cis-muconic acid, respectively. However, the enzyme had a much higher conversion rate for catechol than for 4-chlorocatechol, indicating preference for non-chlorinated substrates. Members of the bacterial consortium were also characterized individually. All isolates were able to assimilate aniline. P. putida C was able to grow on 4CA solely, while S. maltophilia D was able to grow on 4-chlorocatechol. These results suggest that the degradation of 4CA in the presence of aniline by the bacterial consortium was a result of interspecies interactions.