A mutant microbe that generates trace amounts of gold on silver, and uses of the mutant microbe for recovering precious metals and producing biofuels and oil products are described. According to an exemplary embodiment, the mutant microbe is produced by placing metallic silver in an aqueous solution, and adding a species of Saccharomyces to the aqueous solution such that when the species of Saccharomyces comes in contact with the metallic silver, at least a portion of the species of Saccharomyces transforms into the mutant microbe that interacts with the metallic silver and forms a layer comprising a trace amount of nano gold particles on the metallic silver.