RESUMEN
Despite their complexity, ecotoxicological measurements using higher level responses remain a major tool in the assessment of ecosystem integrity. Nevertheless, the past decade saw an increasing number of cell based testing systems have found widespread application in ecotoxicology. One such test is bacterial bioreporters carrying a stress sensitive promoter fused to an easily detectable reporter gene. In the presence of a specific toxic stress,the expression cassette is switched on and the reporter gene is produced. This study evaluated the use of 14 different Escherichia coli bioreporter strains sensitive to different types of toxicity in the assessment of the ecological status of a small river basin in Flanders, Belgium. The river is fed at two geographically separate locations by two distinct and well-described effluents, one from a household sewage treatment facility and one from the discharge of the wastewater treatment facility of a large chemical plant. The results of the bacterial gene profiling assay were related to active biomonitoring results obtained through higher-level responses of caged Dreissena polymorpha, Chironomus riparius, and Cyprinus carpio deployed at the locations sampled for the bacterial assay. The results of the gene induction assay and the active biomonitoring data correlated well and corresponded to the flow dilution data, which is used here as a surrogate forthe chemical pollution gradient present in the river basin.
Asunto(s)
Perfilación de la Expresión Génica , Sedimentos Geológicos/química , Contaminantes Químicos del Agua/toxicidad , Animales , Monitoreo del Ambiente/métodos , Escherichia coli/efectos de los fármacos , Escherichia coli/genética , Genes BacterianosRESUMEN
Because of increasing awareness and legislative demands, there is a demand for the development and use of biological assays for the assessment of the toxicity of chemicals, environmental samples. Recently, a growing number of bacterial reporter assays have been developed and implemented. Nevertheless, little data is published on the performance of these assays in terms of analytical parameters. We present results on a battery of 14 transgenic Escherichia coli strains carrying different promoter::reporter fusions. Growth characteristics and basal expression levels were modeled and fitted, data show that growth curves should be taken into account during test development. Our study shows that the induction profiles reflect the mode of action, e.g., paraquat clearly induces the soxRS operon. The sensitivity of the assay compares well to that of whole organism tests, e.g., fish and Daphnia for polar organics. Metal toxicity is detected less efficiently, e.g., cadmium is detected near the LC50 of carp, considered a relatively insensitive species towards cadmium. The assay variability ranges from 10 to 40% depending on the strain, comparable to that of other bioassays. The variability was shown to be determined by the intrinsic traits of the promoter-strain combination, not by operating conditions.