Adsorption affinity of heavy metals onto bacteria may be related to the electronegativity of metal ions as described by other studies(Merdy et al., 2009; Seco et al., 1997), which reported that attraction between metals and bacteria is higher with greater electronegativity. The selectivity in both single and multi-component solutions is higher for Pb2+than for Cu2+. In addition, the high ionic radius ofPb2+(1.12´˚A) must induce a quick saturation of adsorption sites due to steric hindrance compared with Cu2+(0.70´˚A). These facts could explain the reactivity of Cu and Pb with bacteria surface sites. Pb2+adsorbs onto calcite and, thus, the Pb2+ions move into Ca2+sites,despite the large ionic radius of Pb2+relative to Ca2+(Sturchio et al.,1997).To further confirm the role of MICP in heavy metal bioremediation, remediated sand samples were analyzed by X-ray diffraction (XRD). XRD spectra indicated the presence of cerussite (lead carbonate, PbCO3), otavite (cadmium carbonate, CdCO3),and copper carbonate (CuCO3) crystals as the predominant minerals, as evidenced by the detection of sharp peaks in analysis of bioremediated samples, in contrast to the control, where peaks corresponding to quartz (SiO2) represented the sharpest peaks (Fig. 7).