Isolation and bio-accumulation mechanisms of a Cdresisting bacterium

Key words: 
• Bacillus cereus /
• cadmium /
• isolation /
• accumulation

Abstract: A bacterial strain, named as RC, possessing stronger cadmium resistance and accumulation abilities was isolated from cadmium-contaminated soil. According to its morphological and biochemical characteristics and 16SrDNA sequences analysis, it was identified as Bacillus cereus. Growth curves of RC were analyzed under culture liquid of different cadmium concentrations.The resistance of RC to Zn and Cu was studied. The results show that its resistance mechanisms to different heavy metals are discrepant.The cadmium precipitation and distribution inside and outside the cell were studied with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). With the 150 mg/L cadmium concentration, there were much granular cadmium precipitate on and inside the cell wall, and also precipitate adhering to the surface of the mycelium. Hence, precipitation inside and outside the cell may be an important way of cadmium resistance and accumulation of the bacterium. The accumulation of Cd in the strain was observed by infrared spectroscopy, which indicates the possible functional groups participated during the accumulation of Cd are —OH、—NH、—CO和—CO—NH—,etc.