Biomineralization of gold: Biofilms on bacterioform gold

Bacterial biofilms are associated with secondary gold grains from two sites in Australia. 16Sribosomal DNA clones of the genusRalstoniathat bear 99% similarity to the bacteriumRalstonia metallidurans—shown to precipitate gold from aqueous gold(III) tetrachloride—were present on all DNA-positive gold grains but were not detected in the surrounding soils. These results provide evidence for the bacterial contribution to the authigenic formation of secondary bacterioform gold grains and nuggets.Frank Reith, Stephen L. Rogers, D. C. McPhail, Daryl Web