Accumulation and detoxification of metals by plants and microbes

Abstract

Excessive toxic metal levels in soils pose potential hazards to human and animal health as well as the ecosystem in general. Anthropogenic sources of heavy metal deposition have increased as the result of the Industrial Revolution. Agriculture, mining, smelting, electroplating, and other industrial activities have resulted in the deposition of undesirable concentration of metals, such as As, Cd, Cr, Cu, Ni, Pb and Zn, in the soil. Although trace metals are important part of the soil ecosystem, the accumulation of these metals may be harmful to people, animals, plants and other organisms contacting the soil or groundwater. Unlike many other pollutants, heavy metals are difficult to be removed from the environment as they cannot be chemically or biologically degraded, and are ultimately indestructible. Now-a-days, various heavy metals constitute a global environmental hazard. Use of microorganisms and plants for the decontamination of heavy metals has attracted growing attention because of their low cost and high efficiency. Microorganisms could be used to clean up metal contamination by removing metals from contaminated water, sequestering metals from soils and sediments or solubilizing metals to facilitate their extraction. In this article, we describe how bacteria and plants accumulate and detoxify metal ions, engineering approaches to enhance the metal tolerance, accumulation and detoxification in microorganisms and plants. We also describe bioremediation using symbiosis between plants and microorganisms. © 2007 Springer-Verlag Berlin Heidelberg.