Assessment of Bacterial Communities in Auriferous and Non-Auriferous Soils Using Genetic and Functional Fingerprinting

Understanding the microbial processes affecting the mobility of Au is important in the development of biogeochemical models describing the formation of secondary anomalies and Au grains in soils and deeper regolith materials. This study characterizes bacterial activity in auriferous soils that is linked to the microbially mediated solubilization of Au, as a result of production and consumption of free amino acids, which can form stable complexes with Au. Through the application of 16S rDNA fingerprinting and community level physiological profiling (CLPP), concurrently with Au mobility data, microcosm experiments have demonstrated the role that mobile Au plays in determining the structure and function of bacterial communities in auriferous soils. The bacterial community of auriferous soils displayed genetic differences compared to non-auriferous (background) soils associated with the appearance of Methylocella sp., Arthrobacter sp. and Bacillus sp., as well as functional differences in the utilization of D-Cellobiose, L-Serine, L-Phenylalanine, L-Arginine and N-Acetyl-D-Glucosamine. These results suggest that soil bacterial communities are linked to biogeochemical Au cycling, and that microbial fingerprinting analyses may be used as a screening tool in Au exploration to differentiate auriferous from background terrains.