Cadmium sources, toxicity, resistance and removal by microorganisms-A potential strategy for cadmium eradication

Cadmium (Cd) is one of the most important toxic environmental heavy metals. Cd pollutes the environment mainly from mining, metallurgy industry, pigments and plastic stabilizers, and manufactures of nickel-cadmium batteries. Some important human intoxication sources are food, water, cigarette smoke, and air contamination. Cd exposure has been linked with cancers of various organs in humans while at cellular level, Cd provokes proliferation, differentiation, and causes apoptosis. Cd aggravates the generation of reactive oxygen species (ROS) causing DNA damage. Cd also alters the expression of genes and decreases enzyme activities involved in antioxidant defense systems. Many living organisms have evolved strategies to cope with the Cd stress either through efflux transport systems or biosorption. The present review describes an overview of the cadmium toxicity against living organisms, microbial resistance mechanisms with special emphasis on the efflux systems, antioxidant profiling, and Cd eradication potential exhibited by microorganisms when exposed to Cd +2 . Cd-resistance and bioremediation potential make these microorganisms a good bioresource for green chemistry to exterminate environmental Cd +2 .