Genomics for the understanding of the host-pathogen interaction: the case of the Atlantic salmon and Piscirickettsia salmonis

Abstract

The pollution by industrial and municipal effluents are major sources of concerns. Fish cell cultures were applied in different strategies of the evaluation of effluents, particularly whole toxicity, toxicity identification evaluation and mode of action studies based in adverse outcome pathways. Whole effluent toxicity was evaluated using a battery of five model systems from four trophic levels: Daphnia magna was the most sensitive system, followed by the hepatoma fish cell line PLHC-1, the bacterium Allivibrio fischeri, the fibroblastic fish cell line RTG-2 and the algae Chlorella vulgaris, detecting a risk of eutrofization. The uptake of neutral red was more sensitive than the content of protein assay. The main morphological alterations observed were cell loss, hydropic degeneration, and a general loss of lysosomes and of their perinuclear distribution. The toxicity was characterized in PLHC-1 cells through toxicity identification evaluation, in which a partial reduction with graduation at pH 11, filtration, aeration and addition of thiosulfate or EDTA was shown; on the other hand, a low sorption in solid phase extraction suggested that the main responsible were not organic compounds. Consequently, it was not necessary to apply an effect directed analysis HPLC fractionation. In the chemical identification phase, Zn, Cd, As, Cu and Pb were quantified in decreasing concentrations. In the toxicity confirmation phase, a reconstituted sample and individual solutions, presented decreasing toxicity: Zn > Pb > As+5 > Cd > Cu > As+3, the global toxicity being explained by response addition. In the last step, the mode of action was investigated using five specific biomarkers. While metallothionein and succinate dehydrogenase activity were increased, no changes occurred for lysosomal function, acetylcholinesterase and EROD activities, the responsibility of the toxicity for the elements found being confirmed.