Bioremediation of heavy metal pollution exploiting constituents, metabolites and metabolic pathways of livings. A review

Removal of heavy metals from the soil and water or their remediation from t he waste streams "at source" has been a long-term challenge. During the rec ent era of environmental protection, the use of microorganisms for the reco very of metals from waste streams as well as employment of plants for landf ill applications has generated growing attention. Many studies have demonst rated that both prokaryotes and eukaryotes have the ability to remove metal s from contaminated water or waste streams. They sequester metals from soil s and sediments or solubilize them to aid their extraction. The proposed mi crobial processes for bioremediation of toxic metals and radionuclides from waste streams employ living cells and non-living biomass or biopolymers as biosorbents. Microbial biotransformation of metals or metalloids results i n an alteration of their oxidation state or in their alkylation and subsequ ent precipitation or volatilization. Specific metabolic pathways leading to precipitation of heavy metals as metal sulfides, phosphates or carbonates possess significance for possible biotechnology application. Moreover, the possibility of altering the properties of living species used in heavy meta l remediation or constructing chimeric organisms possessing desirable featu res using genetic engineering is now under study in many laboratories. The encouraging evidence as to the usefulness of living organisms and their con stituents as well as metabolic pathways for the remediation of metal contam ination is reviewed here. A review with 243 references.