Application of a multiple endpoint bacterial reporter assay to evaluate toxicological relevant endpoints of perfluorinated compounds with different functional groups and varying chain length

Perfluorinated compounds are widely distributed in the environment; good knowledge about the toxic mode of action of these compounds can contribute to improved molecular design and risk assessment.The studied compounds were evaluated with a bacterial multiple endpoint reporter assay for responses in four different mode of action classes (oxidative damage, DNA damage, general cell lesions and membrane damage). The results of our study clearly demonstrate that inductions of stress responsive genes occur for the different compounds and confirm some of the known mechanisms of work for well studied compounds like PFOA and PFOS, and in addition provide new information for less studied compounds.Few inductions were observed after exposure to the low carbon number carboxylic acids, PFBtA (CF3(CF2)2C(O)O−), PFPtA (CF3(CF2)3C(O)O−), PFHxA (CF3(CF2)4C(O)O−) and PFHpA (CF3(CF2)5C(O)O−) at equimolar concentrations (0.0156–1 mM). The induction of membrane damage markers (MicF and OsmY) is prominently present after exposure to PFOS (CF3(CF2)7SO3-) and even more after exposure to PFNA (CF3(CF2)7C(O)O−).This is the first report describing the mode of action of carboxylic acids with 11 and 12 carbon atoms; they are equally potent inducers relative to PFOS and PFNA. Overall, the effects seen at the level of gene expression were higher for the sulfonic acids than for the carboxylic acids, but the effect of the chain length is more important than the effect of the functional group.