ABSTRACT
Acknowledgment............................................................................................................................337 References ......................................................................................................................................337
Metals are ubiquitous in environments and are essential to organisms, e.g., K, Na, Mg, Ca, Mn, Fe, Co, Ni, Cu, Zn, and Mo; other metals have no known essential biological functions, e.g., Al, Ag, Cd, Sn, Au, Sr, Hg, and Pb [1]. All these elements can interact with microorganisms and be accumulated by physicochemical mechanisms and transport systems associated with cell growth and metabolism [2,3]. Heavy metals are not biodegradable and tend to be readily accumulated in living organisms, causing various diseases [4-6]. Virtually all metals can exhibit toxicity to above certain threshold concentrations whether essential or nonessential [1,7].
