Bacteria Point The Way To Gold Deposits

“Experimental results showed that relatively high numbers of B. cereus spores were associated with gold-containing soils, which suggested the possibility of B. cereus serving as a biogeochemical indicator of underlying gold deposits. This bioindex system may help geologists to locate the gold deposits at low cost and with improved efficiency,” says Dr. Hongmei Wang of Ohio State University, one of the researchers on the study, which was presented at the 102nd General Meeting of the American Society for Microbiology.

With the support of the Ministry of Land and Resource and Ministry of Education of China, Dr. Wang and her collaborators had been working on microbial exploration in northwest Sichuan province, which is very famous for its abundance of gold resources. The four-year project was for her Ph.D. thesis research.

Usually gold in soluble form is toxic to microbes as well as to higher organisms. However, bacterial spores can resist harsh environmental conditions (e.g., heat, toxic chemicals, UV radiation, and desiccation) better than bacteria in normal growing stage. In auriferous (gold-containing) soils, microorganisms that can form spores will stand a better chance to survive. In this study, high numbers of B. cereus spores were found in areas of gold-containing orebodies, and they were two or three orders of magnitude higher than those in the background areas. Based on high spore numbers and their distribution patterns, mineralized areas of gold-containing deposits can be determined and the corresponding orebodies can be located if the B. cereus-based assay is combined with other exploration methods.

Experiments on the interaction between B. cereus and gold ion showed that low concentrations of gold do not affect the spore formation of B. cereus. However, when gold concentration was increased, the spore formation of B. cereus was induced, which may explain high spore numbers in gold-containing areas.

“This biotechnique will help exploration and mining companies search for underlying gold deposits with relative high gold grades. The analysis of B. cereus in the soil is simpler and cheaper than chemical methods of elemental analysis of soils and rocks. The method is, therefore, promising for the potential application in geoexploration accompanied with routine geochemical and geophysical methods,” says Dr. Wang.