**3.2 Nano bioremediation of heavy metals**

The major global concern is contamination of heavy metals because of their toxicity and threat to flora and fauna [36]. Anthropogenic activities are the main cause for pollution of heavy metals. There are 65 groups of heavy metals which can be distinguished on a number of criteria, like cationic- hydroxide formation, specific gravity >5 g/ml, complex formation, hard- soft acids and bases, eutrophication and environmental toxicity. Higher doses can cause birth defects, cancer, skin lesions, retardation, major organ damage such as liver and kidneys [37]. Industries of electroplating, cement, paint, etc. discharges heavy metals such as Cd, Cu, Pb, Hg, Ni, Zn and As which are highly toxic to living organisms. The waste water is directly discharged to water bodies without any prior treatment. These can cause serious mutations and Physiological damages to organisms of habitat [38].

If possible, we will be pleased to have uses of microbes in bioremediation of toxic heavy metals with interest of nanofabrication of environmentally useful submicron scale particles. In that condition, microbes can be utilized in an eco-friendly and effective remediation of heavy metals [39].

There are mainly three attributes of nanotechnology which are being used in nanobioremediation-


Nanobioremediation prefers in-situ treatment of contaminants because it's economical, highly efficient and can be applied on larger scale [42].
