Metallophiles and Heavy Metal Bioremediation

Heavy metals, a group of naturally occurring elements present throughout the earth’s crust are known to have wide biological implications. Anthropogenic activities cause constant augmentation of heavy metals having a tremendous negative impact on life forms in the environment with levels beyond safety. Microorganisms invariably are the first group of organisms that are directly impacted by the accumulation of heavy metals in the environment. Heavy metal toxicity is pronounced amongst microbes which impacts change in microbial community composition and function in any ecosystem. The intrinsic and acquired resistance properties have led to the development of resistant bacterial communities in contaminated areas. A large number of heavy metal tolerant bacteria have been isolated from various polluted sites like industrial effluents, aquaculture, agricultural soils, foods, river water and sediments. The determinants of resistance are both plasmid and chromosomal encoded in bacteria. Amongst the various strategies of survival mechanisms employed by bacteria, efflux system and enzyme detoxification are two general mechanisms supplemented occasionally by resistance mechanisms like sequestration or bioaccumulation. These strategies of resistance in bacteria are generally exploited in bioremediation strategies. Due to the persistent nature and non-degradability of heavy metals, it becomes difficult to clean up the pollutant from the environment and moreover, the conventional treatments for heavy metal pollution are complicated and cost-intensive. Therefore, microbial-based technology furnishes effective, economic and eco-friendly applications for the bioremediation of heavy metals from contaminated environments.