Construction and application of an Escherichia coli bioreporter for aniline and chloroaniline detection

Aniline and chlorinated anilines (CAs) are classified as priority pollutants; therefore, an effective method for detection and monitoring is required. In this study, a green-fluorescence protein-based bioreporter for the detection of aniline and CAs was constructed in Escherichia coli DH5 alpha, characterized and tested with soil and wastewater. The sensing capability relied on the regulatory control between a two-component regulatory protein, TodS/TodT, and the P (todX) promoter of Pseudomonas putida T-57 (PpT57), since the gene expression of todS, todT, and todC2 are positively induced with 4-chloroaniline. The bioreporter system (DH5 alpha/pPXGFP-pTODST) is markedly unique with the two co-existing plasmids. The inducibility of the fluorescence response was culture-medium- and time-dependent. Cells grown in M9G medium exhibited a low background fluorescence level and were readily induced by 4CA after 3-h exposure, reaching the maximum induction level at 9 h. When tested with benzene, toluene, ethyl-benzene and xylene, aniline and CAs, the response data were best fit by a sigmoidal dose-response relationship, from which the K (1/2) value was determined for the positive effectors. 3CA and 4CA were relatively powerful inducers, while some poly-chlorinated anilines could also induce green fluorescence protein expression. The results indicated a broader recognition range of PpT57'sTodST than previously reported for P. putida. The test results with environmental samples were reliable, indicating the potential application of this bioreporter in the ecotoxicology assessment and bioremediation of areas contaminated with aniline- and/or CAs.