Investigating copper toxicity in Caenorhabditis elegans.

Increases in global industrialisation are causing a growing release of pollution into the environment. Pollution, particularly by heavy metals is a significant problem as they are non-biodegradable, thus able to accumulate in ecological systems. The heavy metal copper (Cu) though toxic in excess is also an essential trace element that serves as a cofactor in many critical biological processes such as respiration, iron transport and oxidative stress protection. It is therefore important to assess the effects of Cu toxicity on the ecosystem and its natural communities, as environmental pollution impacts on an organism's genomic utilisation resulting in consequences for its biology and thus ultimately affecting population dynamics. Therefore the overall objective of this project was to investigate Cu homeostasis and toxicity using the soil dwelling nematode, Caenorhabitis elegans as a model organism. The effects of Cu toxicity on the population dynamics of C. elegans was determined by investigating changes in life cycle traits. The whole organism response to Cu toxicity was investigated in C. elegans and the EC50 and LC50 of CUSO4 was determined, along with the effects of Cu on growth and development. Cu tolerant mutants were created and phenotypic effects examined among them in order to assess adaptive responses to heavy metal exposure. To enhance our understanding of the complexities of Cu homeostasis at the genetic level the expression profile and functional significance of two putative Cu transporters Ctr and CutC were analysed. Using QPCR technology both genes were found to be down regulated with increasing CuSCU concentrations. RNA-mediated interference (RNAi) technology was exploited to create knockdowns of Ctr and CutC which resulted in significant differences in the C. elegans life cycle in the presence and absence of Cu. Overall RNAi of Ctr and CutC resulted in different demographic and phenotypic effects in C. elegans, indicating at their different roles in Cu metabolism, with Ctr postulated to be a high affinity Cu importer and CutC possibly with a complex role in regulation of Cu proteins. In Summary Cu homeostatis is a complex process maintained by the interactions of many interconnected, but also independent components to ensure that concentrations of this essential yet toxic element are tightly controlled