Metallic species mobilized and released into the environment by the technological activities of human tend to persist indefinitely, circulating and eventually accumulating throughout the food chain, thus posing a serious threat to the environment, animals and humans. It is essential to realize that the metal is only removed from solution when it is appropriately immobilized. Apart from slow natural process of metal mineralization, ultimate removal is attained only when the metal becomes concentrated to the point that it can be either returned to the process or resold. The metallic pollutants can be sorbed by biosorbant material. The mechanism of biosorption is complex, mainly ion exchange, chelation, adsorption by physical forces, entrapment in inter and intrafibrilliar capillaries and spaces of the structural polysaccharide network as a result of the concentration gradient and diffusion through cell walls and membranes. Due to the extensive research and significant economic benefits of biosorption, some new biosorbant resources are poised for commercial exploitation.

Biosorption can be an effective technique for the treatment of heavy metal bearing waste water resulting from human and industrial activities. Several gram positive and gram negative bacteria have the ability to remove the heavy metals, thereby making water contaminant-free. It has been reported that attenuated bacterial biomass has greater biosorption capability than viable cells. Remediation of co-contaminated sites with organic and metallic pollutants is a complex problem, as the components must be differently treated, yet 55% of the hazardous waste sites are co-contaminated (Sandrin and Maier, 2003). Alternatively, the area may be capped to prevent metal-transporting, or to reduce metal mobilization by anaerobiosis or organic matter and clay additions, or environmental pH changes (Sandrin and Maier, 2002) that determine ions bioavailability and affect the biota. In either case, metal removal or stabilization is likely to be the first step to detoxificate co-contaminated sites, as inorganic pollutants in the ionic forms inhibit remediation through interaction with enzymes directly involved in biodegradation (e.g., specific oxygenases) or in general, metabolism, by binding to the enzymes sulfhydryl groups. Unfortunately, few studies provide information on the metal levels that decreased the biotransformation due to the wide range of reported concentrations, and different experimental protocols ions bioavailability and toxicity. Algae, bacteria and fungi and yeasts have proved to be potential metal biosorbents (Volesky, 1986).

Biotechnology Journal, Stress Adaptation of Bacteria, Extremophiles, Bacterial Adaptation, Cytosolic Components, Denature Cellular Proteins, Reactive Oxygen Species, Monounsaturated Fatty Acids, Ultraviolet Radiation, Environmental Stress, Stress Management, Biological Systems, Cellular Economy.