Gamma-hexachlorocyclohexane (ɣ-HCH), commonly referred to as lindane, is one of the most widely studied and ubiquitously detected organochlorinated contaminants within the environment. Mainly used as a pesticide, it is highly resistant to chemical, biological and natural photolytic light degradation which enables it to remain intact for long periods of time. Concerns over its toxicity, persistence and long-range transport have necessitated an environmentally appropriate and cost-efficient remediation strategy to remove it from the ecosystem, especially in developing countries where consumption and production of Lindane can have a serious effect on health, economics and arable land use. Phytoremediation, using plants and their respective enzymes, is an eco-friendly, practical and cost efficient biotechnology for the treatment and removal of lindane. This thesis aims to develop a detailed understanding of transgenic Arabidopsis thaliana expressing an HCH-dehydrochlorinase (LinA) protein, from Sphingobium japonicum UT26, and its ability to take up, dechlorinate and mineralize the persistent organic pollutant.
This investigation of transgenic phytoremediation utilizes Gateway® cloning technology, Agrobacterium-mediated transformation, enzymatic activity assays, along with metabolomic and proteomic techniques to show that transgenic A. thaliana can express the bacterial protein and is capable of removing lindane from its environment to either sequester it or metabolize it in vitro. However, this work also establishes that in vivo, the transgenic plant displays similar growth characteristics to the wild type and is unable to survive on any of the lindane concentrations previously estabilished as being toxic to A. thaliana.. Therefore, additional investigations into the metabolome and interactome of transgenic A. thaliana, and other plants exhibiting an innate ability to uptake lindane, as well as the controlled expression of engineered proteins, need to be studied before confirming the effectiveness of phytoremediation as a suitable technology for the removal of lindane from the environment.
