ABSTRACT
Environmental pollution by heavy metals is a result of human activities such as power transmission, electroplating, smelting, mining, energy and fuel production, intensive agriculture, melting operations, and sludge dumping. It is a global problem affecting not only the environment but also human health. Conventional remediation strategies are either expensive or they generate toxic by-products that also adversely affect the environment. Therefore, environmental safety requires biological techniques. One such technique is bioremediation. Bioremediation primarily uses microorganisms or microbial processes to transform heavy metals into less toxic or harmless forms. Bioremediation can either be carried out in situ or ex situ, depending on site characteristics, and the type and concentration of pollutants. Microorganisms exhibit a number of metabolism-dependent and -independent processes for the uptake and accumulation of heavy metals and radionuclides. Different mechanisms of heavy metal microbial remediation are bioaccumulation, biosorption, biotransformation, metal-microbe interactions, biomineralization, and bioleaching. By these mechanisms, microbes restore heavy-metal-contaminated environment. This chapter discusses the mechanisms of heavy metal accumulation and bioremediation of such contamination by microorganisms.
