Biomineralization of Se Nanoshpere by Bacillus Licheniformis

Biological dissimilatory reduction of selenite (SeO₃ ²⁻) to elemental selenium (Se⁰) is common,but the mineral formation and the biogenic process remain uncertain. In this study,we examined the Se⁰ formation during the selenite bioreduction by Bacillus licheniformis SeRB-1 through transmission electron microscope (TEM),energy-dispersive spectrometry (EDS) and X-ray absorption fine structure (XAFS) techniques. Results showed that the reduction process occurred mostly during the exponential phase and early stationary phase,whilst the elemental selenium was produced in these periods. From the TEM images and polyacrylamide gel electropheresis,it is known that the Se⁰ granule formation is a biologically-induced type,and the cell envelopes are the main biomineralization positions,and particles may go through a process from nucleation to crystallization,under the control of microbes. In fact,the minerals are spherical nanoparticles,occurring as a microcrystal or amorphous form. It is vital to recognize which kinds of proteins and/or polysaccharides act as a template to direct nanoparticle nucleation and growth? This should focus for further studies. This study may shed light on the process of formation of Se(0) nanosphere.