The Interaction Mechanism Between Bacillus Cereus And Gold

Metal mineral resources play an important role in economic development.With the continuous exploitation and utilization of mineral resources,surface deposits are gradually depleted.An efficient method for new concealed deposits exploration is increasingly important.Microbial mineral exploration is of great interest to the minerals industry.In this study,we investigated the possibility of using B.cereus in the soil from Jiaodong Gold Mine as a biogeochemical indicator for gold prospecting.Scanning electron microscopy(SEM),transmission electron microscope(TEM),X-ray Absorption Near Edge Spectroscopy(XANES)techniques and X-ray photoelectron spectroscopy(XPS)were used to investigate the reducing capability and detoxification mechanisms of the B.cereus strain in the environment containing Au.The result of this thesis mainly includes:(1)In the soils collected from Jiaodong gold deposit,the numbers of Bacillus cereus spores were significantly correlated with the concentrations of Au(efficient R2=0.78),but not with that of the other elements,such as Zn,As,Cd,Cu and Pb,which indicated that Bacillus cereus can be used as an indicator in the exploration of Au deposits.(2)Bacillus cereus can dissolve up to 45.90%Au after 7d of incubation,while the numbers of Bacillus cereus spores were significantly higher than that of the control group by about 10-25 times.The dissolution and liberation of gold in the auriferous ore could be responsible for the increase of Bacillus cereus spores.(3)The growth of Bacillus cereus was not affected when Au(?)concentration was below 0.6 ?g/mL,but the numbers of spores increased.At Au(?)concentrations higher than 0.6 ?g/mL,the growth of Bacillus cereus was inhibited.(4)Toxic Au(?)was reduced to nontoxic Au nanoparticles by B.cereus.Spherical Au nanoparticles were deposited on the surface of cells and in the cytoplasmic regions.XANES results showed that Au(?)-S intermediate was generated during the reduction process.The detoxification process of Au(?)was mainly mediated by cytoplasm rather than the bacterial excreta.Bacillus cereus forms spores with a multilayer protective structure to protect themselves and release lysate to participate in the detoxification process,which greatly improves the survival of Bacillus cereus.(5)XPS results showed that C-OH?C-O-C and N-C=O may participate in Au(?)reduction and detoxification process.Au4f suggested that cellular Au was reduced to Au(?)species intermediates,and finally leading to the formation of Au(0),which was consistent with the results of XANES.