Genetic Construction of Novel Metabolic Pathways: Degradation of Xenobiotica

Abstract

Photosynthetic microorganisms and plants are responsible for fixing carbon dioxide and thus for channeling inorganic carbon into the complex organic compounds of which living systems consist. The organic constituents of organisms are generally biodegraded, either to simpler organic compounds which serve as precursors for the synthesis of new complex molecules, or to inorganic carbon compounds such as CO₂, thereby completing the carbon cycle. Organic carbon may cycle through a number of different living organisms before finally being mineralized to CO₂. Soil and water microorganisms are important agents of biodecomposition and thus play a crucial role in recycling carbon and in maintaining the biosphere in equilibrium. Organic materials, however, may not necessarily be degraded but instead become converted to new organic compounds under the influence of geophysical and geochemical processes, and thereby exit from the carbon cycle for a period of time. The return to the carbon cycle of material sequestered in coal and oil deposits, etc. occurs through further geological processes and human activities that expose it to the biodegradative activities of microorganisms or that result in its combustion.