Gene expression profiling to characterize sediment toxicity – a pilot study using Caenorhabditis elegans whole genome microarrays

In this pilot study, we exposed the nematode Caenorhabditis elegans to three sediments of German rivers with varying (low, medium and high) levels of heavy metal and organic contamination. Beside chemical analysis, three standard bioassays were performed: reproduction of C. elegans, genotoxicity (Comet assay) and endocrine disruption (YES test). Gene expression was profiled using a whole genome DNA-microarray approach to identify overrepresented functional gene categories and derived cellular processes. Disaccharide and glycogen metabolism were found to be affected, whereas further functional pathways, such as oxidative phosphorylation, ribosome biogenesis, metabolism of xenobiotics, aging and several developmental processes were found to be differentially regulated only in response to the most contaminated sediment.This study demonstrates how ecotoxicogenomics can identify transcriptional responses in complex mixture scenarios to distinguish different samples of river sediments.It is a well established fact that the water quality of rivers is strongly influenced by their sediments. Sediments are frequently highly contaminated because hydrophobic chemicals, introduced to the water body, bind to particles and accumulate in the sediment. In contrast to surface waters, river sediments therefore reflect not only present, but also past contamination. Ignoring their capacity to act as a sink and as a potential source of contamination can lead to wrong conclusions concerning the characterization of current pollution levels. Therefore, sediment quality assessment has to be included as an essential integral part of any environmental risk assessment of freshwater bodies [1].Detailed chemical analyses and sediment toxicity tests typically expose benthic organisms to bulk sediments to assess their quality [2]. The diversity of toxic substances in the environment, the complexity of possible adverse or even positive responses to exposure, and various biotic and abiotic factors th