Microbial Bioremediation of some Heavy Metals in Soils: An updated review

Nowadays, due to industrialization and extraction of natural resources, soil and water pollution is one of the major global concerns. During the recent era of environmental protection, the use of microorganisms for the recovery of heavy metals from soil, sediments and water as well as employment of plants for landfill applications has generated growing attention. The role of microorganisms and plants in biotransformation of heavy metals into nontoxic forms is well-documented, and understanding the molecular mechanism of metal accumulation has numerous biotechnological implications for bioremediation of metal-contaminated sites. The food and water we consume are often contaminated with a range of chemicals and heavy metals, such as gold, copper, nickel, zinc, lead, cadmium, arsenic, chromium, and mercury that are associated with numerous diseases. Human activities like metalliferous mining and smelting, agriculture, waste disposal or industry discharge these metals which can produce harmful effects on human health when they are taken up in amounts that cannot be processed by the organism. Many studies have demonstrated that microbes have the ability to remove heavy metals from contaminated soils. Among others some of the microorganisms that play great role in bioremediation of heavy metals are Pseudomonas spp.Alcaligenes spp., Arthrobacter spp., Bacillus spp., Corynebacterium spp., Flavobacterium spp., Azotobacter spp., Rhodococcus spp.Mycobacterium spp., Nocardia spp., Methosinussp.,Methanogens, Aspergilusniger, Pleurotusostreatus , Rhizopusarrhizus, Stereumhirsutum, Phormidiumvalderiumand Ganodermaapplantus. The encouraging evidence as to the usefulness of microorganisms and their constituents for the remediation of heavy metals from contaminated soils is reviewed in this article. Keywords: Bioremediation, Biotransformation, Heavy metals, Microbial, Toxicity.