Degradation of aniline and monochlorinated anilines by soil-born Pseudomonas acidovorans strains

Abstract

Four bacterial strains (CA26, CA28, CA37, and CA45), which all were able to use aniline, 3-chloroaniline (3-CA), and 4-chloroaniline (4-CA) as sole sources of carbon, nitrogen and energy, were isolated after enrichment in aerated soil columns and identified as Pseudomonas acidovorans strains. In addition strains CA26 and CA45 were able to degrade 2-chloroaniline (2-CA) at very low rates. At 25°C strain CA28 was grown on aniline and 3-CA with generation times of 3.0 and 7.7 h, respectively, and exhibited complete mineralization of these substrates in degradation rates of 2.25 mmol aniline and 1.63 mmol 3-CA g^-1 of biomass per hour, respectively. Degradation of 4-CA occurred at 1.54 mmol 4-CA g^-1 of biomass per hour and a generation time of 18.7 h but, in contrast, was not complete due to formation of minor amounts of chlorohydroxymuconic semialdehyde, a meta-cleavage product of 4-chlorocatechol. The initial attack on the substrate, the formation of corresponding chlorocatechols from 3-CA and 4-CA, was found to be the rate-limiting degradation step. Evidence for two different aniline-oxygenase systems in strain CA28 with distinct activity pattern on chlorinated and nonsubstituted anilines was demonstrated by oxygen uptake rate experiments with aniline and chloroaniline pregrown cells. Further degradation was shown to be initialized by catechol dioxygenases.