Ecotoxicity testing and remediation potential of petroleum components : use of diagnostic luminescent biosensors
The bacteria E. coli HB101, E. coli DH1 and P. fluorescens 10586r were lux marked with the multicopy plasmid pUCD607. P. putida F1, was chromosomally marked by the insertion of the mini-Tn5 transposon. Growth and bioluminescence of E. coli HB101, E. coli DH1 and P. fluorescens 10586r were characterised and optimised for freeze-dried cultures (E. coli HB101 and E. coli DH1). The toxicity of aqueous solutions of MTBE, benzene and naphthalene was investigated using the biosensors, E. coli HB101, E. coli DH1, P. fluorescens 10586r pUCD607, and luc-marked, S. cerevisiae. The biosensors responded to high environmental concentrations. The EC50 values were comparable for E. coli DH1 and P. fluorescens 10586r. The yeast was shown to be quite resistant to MTBE. There is a general use of solvents, such as DMSO, to solubilise or extract compounds with high octanol water partition coefficients. This has a distorted effect on their actual toxicity. This was shown by the development of QSARs using the toxicity response of E. coli HB101 and plotting this against hydrophobicity. Bioluminescent based biosensors are useful tools not just only to assess toxicity but also to allow quantification and prediction of the remediation potential of certain compounds which enables a more complete assessment of their impact. A catabolic biosensor, P. putida TVA8, was used to further investigate pollutant relations. Correlating E. coli DH1, P. putida F1 QSARs with a QSBR developed for P. putida TVA8 allowed a better understanding of enzymatic specificity and toxicity. To evaluate the fate of MTBE in the environment it is necessary to investigate how it interacts with other co-contaminants. The determination of interactions is crucial to assessing environmental damage. Using the biosensor response and a model it was possible to investigate the nature of interactions. For MTBE:benzene mixtures, there was no increase in combined toxicity to E. coli DH1 and P. fluorescens 10586r. E. coli HB101 response had a different pattern and for low concentrations of MTBE:benzene synergistic interactions were observed. For MTBE:naphthalene, overall, the effect was additive. The toxicity of petrol containing MTBE was assessed since this is the major source of introducing MTBE in the environment. MTBE did not change the toxicity of petrol to the receptor tested. To assess the toxicity of MTBE's degradation products, E. coli DH1 was used. Most of MTBE degradation products were less toxic than MTBE, although TBF and formaldehyde had lower EC50 values. MTBE's effect as a solvent on co-contaminant specific biosensors was evaluated. MTBE changed the cell permeability in P. fluorescens HK44. Nevertheless P. putida TVA8 an E. coli DH5a showed no induction.