CHARACTERIZATION OF CADMIUM-RESISTANT BACTERIA ISOLATED FROM POLLUTED SOILS IN ALGERIA, AND EVALUATION OF CADMIUM REMOVAL, USING LIVING FREE AND IMMOBILIZED CELLS

Soil pollution by heavy metals is one of the most important problems around the world. Microorganisms in these environments develop various mechanisms of resistance and become able to accumulate these metals. In this study, twenty-three cadmium-resistant bacteria were isolated from three soils and characterized. Two of them (YL-SS8, YL-553), highly cadmium-resistant, were selected and identified by the sequencing of the 16S rRNA gene, then tested for their ability to remove cadmium ions. The results revealed that the characterized bacteria belonged to nine families and ten genera, while the most resistant are authentically identified as Bacillus infantis and Pseudomonas fluorescens. The MIC of bacteria ranged from 500 mu g.mL(-1) to 1100 mu g.mL(-1), Bacillus infantis and Pseudomonas fluorescens showed MIC of the order of 1100 mu g.mL(-1) and 900 mu g.mL(-1) respectively. The free living cells of B. infantis accumulated about 90 mu g.mL(-1) of cadmium, whereas those of P. fluorescens 81 mu g.mL(-1) after 24 hours of contact. During the same time, the immobilized cells accumulated quantities slightly better with respective values of 93 mu g.mL(-1) and 85 mu g.mL(-1). Due to their strong resistance and high cadmium removal capacity, the two bacterial isolates could be exploited for biotechnological remediation of cadmium and other heavy metals from contaminated soils.