Evaluation of Short-Term Toxicity of Treated Sewage with Biological Response and Comprehensive Gene Expression Analysis in Zebrafish Embryos and Sac-Fry Larvae

Abstract

 In this study, secondary treated sewage was used in a short-term toxicity test on zebrafish embryo and sac-fry stage larvae. The relationship between biological responses such as hatch/survival rates and comprehensive gene expression changes, effect on reduced of gene expression by dilution and ozonation treatment were investigated. The levels of gene expression in fish exposed to treated water were compared with those exposed to river water as a control. The highest concentration of secondary treated sewage used (80％) did not appear to influence the hatch rates or survival rates of zebrafish, however, gene expression was altered. The number of differentially expressed genes decreased with reduction in percentage of secondary treated sewage used. Gene ontology (GO) enrichment indicated immunity, metabolism, stress response, and signal transduction pathways were affected by secondary treated sewage. A ten-fold dilution or ozonation treatment of secondary treated sewage demonstrated reduction of these effects on gene expression at level equivalent to these of river water controls.