To assess the impacts of man-made extremely low-frequency electromagnetic field (ELF-EMF) on soil ecosystems, the soil nematode was applied as a biological indicator to characterize ecotoxicity of ELF-EMF. In this paper, a soil-living model organism, Caenorhabditis elegans (C. elegans) was exposed to 50 Hz, 3 mT ELF-EMF. The integrated lipidome, proteome and transcriptome analysis were applied to elucidate physiological acclimations. Lipidomic analysis showed that ELF-EMF exposure induced significant alterations of 64 lipids, including significant elevation of triacylglycerols (TGs). Proteome results implied 157 changed protein expressions under ELF-EMF exposure. By transcriptomic analysis, 456 differently expressed genes were identified. Gene Ontology (GO) function and pathway analyses showed lipidomic alteration, mitochondrial dysfunction and the stress defense responses following ELF-EMF exposure in C. elegans. Conjoint analysis of proteome and transcriptome data showed that a higher expression of genes (sip-1, mtl-1 and rpl-11.1, etc.) were involved in stress defense responses to ELF-EMF exposure. These results indicated that ELF-EMF can induce effects on soil nematodes, mainly through disturbing lipid metabolism such as increasing TGs content, and eliciting stress defense responses. This study provided a new understanding in ELF-EMF exposure effects on soil nematodes and suggested a potential way of interpreting ELF-EMF influences on soil ecosystems.

GO enrichment and IPA pathway analysis. (A) Differential proteins (ELF-EMF vs Control). Red indicates upregulation, and green indicates downregulation (B) Differently expressed genes. Red and green plots represent genes with significantly different expression; blue plots represent those showing no significant difference. (C) GO analysis of differential proteins. Top ten terms of each GO category were shown. Each Column means the enriched protein numbers. Column color depth indicates the enriched degree. (D) IPA analysis of proteomic data. Top 10 enriched pathways were shown. (E) IPA analysis of transcriptomic data. Threshold was set as P<0.05 (means –log (p-value) >1.31). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)