Bacillus cereus, a geobiological marker for gold prospecting isolated from soil from the Jiaodong Gold Mine

Abstract

An efficient method for new gold deposits exploration is of great interest as the existing deposits depleted. In this paper, we investigated the possibility of using B. cereus in the soil from Jiaodong Gold Mine as a biogeochemical indicator of gold. Cell counting, growth curve assay, SEM/TEM-EDS and X-ray Absorption Near Edge Spectroscopy (XANES) techniques were used to investigate the sporulation characteristics, reducing capability and detoxification mechanisms of the B. cereus strain in the environment containing gold. The results showed that: (1) The frequencies of B. cereus spores were higher in areas where elevated concentrations of Au were detected, which was not observed for other elements, such as As, Cu, Zn, Cd and Pb. (2) B.cereus has the ability to facilitated the solubilization of Au. The dissolved gold subsequently stimulated B.cereus spores formation, and mother cells release the contents of their cytoplasm to ameliorate gold toxicity. (3) Toxic Au (III)-complexe was reduced to nontoxic Au (0) nanoparticles by B. cereus. Before reduced to Au (0), cellular Au was coupled with the formation of AuS intermediate species. The results showed that B.cereus spores were confirmed to exist in the gold mine soil, and the reduction and detoxification of gold were mediated by the cytoplasm released by the mother cells, which led to the formation of gold nanoparticles.