Health effects of heavy metal contaminants Vis-`a-Vis microbial response in their bioremediation

Toxic heavy metals are currently significant environmental pollutants as their growing ecotoxicity becomes a serious public health concern. Their multiple application in several fields such as the mining industry, agriculture, medicine, technology and many others, leads to a widespread distribution into the environmental systems. Since toxic metals are not biodegradable, their accumulation in soil, water and air contaminates the food chain, which poses a danger to human health. Because of extensive damage caused by metal intoxication on various organs of the human body, the search for therapeutic methods is very important. Removal of heavy metals from the body is usually carried out by the most common and conventional chelation therapy methods. However, for removal from environment the use of chemical methods is often expensive and can lead to the production of secondary pollutants. There is a remarkable attentiveness with respect to recent progress in heavy metals remediation over the past few decades with special emphasis on bioremediation utilized in various environmental areas. The present review is focused to throw light on the possible sources and related intake routes of the harmful metals, the symptoms of poisoning, their impact on the environment and health and the molecular mechanisms, which threaten human health effects. It also aims to provide an overview of the available studies on microbial bioremediation of heavy metals from the environment, including the mechanisms involved in metal removal and some future directions in microbial biodegradation technology.