Selection of microorganisms for bioremediation of agricultural soils contaminated by cadmium

Abstract

Accumulation of toxic metals in agricultural soils is an issue of health concern because toxic metals may be transferred to plants and food. The reclamation of metal-polluted soils, e.g. by using chemical extractants, is usually difficult and incomplete. An alternative option is to try to decrease the transfer of heavy metals from soil to plant by inoculating the soil with microorganisms selected for their ability to biosorb heavy metals. Here, we isolated one fungus, two actinomycetes and two bacteria from soil contaminated by cadmium. These microbes were found to grow in the presence of high cadmium level in laboratory conditions. The fungus and the actinomycetes have the best growth capacity in the soil extract in presence of 10 mg Cd l-1 which is representative of their ability to soil colonization. The bacillus, despite a low resistance to high cadmium concentrations, is very efficient in presence of 1 mg Cd l-1. The percentage of cadmium biosorbed in the medium (up to 50% in presence of 10 mg Cd l-1) and the specific biosorption (80 to 140 mg Cd g-1 of biomass) led to determine that one actinomycete and the bacillus are the most efficient microorganisms that will be used to later bioremediation experiments in soil microcosms. © 2005 Springer-Verlag Berlin Heidelberg.