Dose–response relationships and statistical performance of a battery of bacterial gene profiling assays

Abstract

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.

Eco-, geno- and human toxicology of bio-active nanoparticles for biomedical applications

“…The results of the gene expression studies are represented as fold inductions, the activity of the gene at concentration x divided by the activity of the gene of the control. Fold inductions were considered significant (Dardenne et al, 2007) on the basis of the following criteria: (1) presence of a dose-response relationship (R 2 > 0.50, significant at p < 0.05 for six degrees of freedom) and a positive slope different from 0 (p < 0.05) in a linear model, (2) signal different from and higher than the blank confirmed by Dunnett's test (p < 0.05).…”

“…The bacterial gene profiling assay was performed as described in Dardenne et al (2007). In total, 14 different Escherichia coli strains, with different stress gene promoters (KatG,MicF,OsmY,UspA,RecA,Zwf,ClpB,UmuDC,MerR,Ada,DinD,Soi28,Nfo and SfiA) were used.…”

Assessment of toxic potential of three different heavy metals to Clarias batrachus (Linn.) utilizing static acute bioassay

“…The percent mortality observed for each dose was calculated and converted to probits by means of a probit (Finalayson and Verrue, 1982;Hansen et al, 2002), guppy, Poecilia reticulata (Yilmaz et al, 2004), Cyprinus carpio (Muley et al, 2000;Dardenne et al, 2007), Nile tilapia, Oreochromis niloticus (Garcia et al, 2006) and Rohu, Labeo rohita (Dutta and Kaviraj, 2001). In the present research work, Finney's Probit Analysis for evaluating the acute toxicity response gave 96 hour LC 50 value for C. batrachus exposed to CuSO 4 .5H 2 O as 15 ppm, Pb(C 2 H 3 O 2 ) 2 29 ppm, CdCl 2 35 ppm.…”

Bacterial gene profiling assay applied as an alternative method for mode of action classification: Pilot study using chlorinated anilines

“…One strain (PQ37), from the SOS chromotest and referred to as SfiA, was added to the original setup [21]. The coefficient of variation and the analytical performance of the assay were previously shown to be of good quality and comparable to other bioassays [22]. The stress gene promoters respond to a variety of chemical stress conditions and can be subdivided into general endpoint or MOA classes: membrane damage, protein perturbation, DNA damage, metal presence, oxidative, osmotic and cellular stress.…”

“…The detailed protocol of the assay has been extensively described by Dardenne et al [22]. In brief, after an overnight culture of the stocks, inoculation of the bacteria in 96-well sterile multititer plates was performed in triplicate in three separate plates.…”