Bacterial strategies for obtaining chemical energy by degrading sulfide minerals

Sulfide leaching bacteria, which are used in mining operations have originally evolved to maximize their chemical energy gain from dissolving inorganic metal sulfides. Depending on whether they were only adapted to oxidize Fe2 e.g.Leptospirillum ferrooxidans or whether they could do both, oxidize Fe2 and the much more energy rich sulfur species e.g. Acidothiobacillus ferrooxidans , they have developed different strategies towards the disintegration of crystallized metal sulfide. They have also learned to take advantage of symbiotic leaching processes in which different bacterial species generate a synergetically enhanced leaching activity. Light and electron microscopical studies of leaching activities, in which interfacially active bacteria are prospering, also reveal a coupled bacterial activity in close homogeneous environment. Colloidal nanoparticles appear to support leaching activity. There is evidence that they have the ability to provide both an accessible energy source for bacteria and to warrant ongoing reactivity for the leaching process. The latter is basically due to the higher surface reactivity of colloids that allows for faster reaction times. In this report pyrite is used as a model mineral for discussing evolved bacterial strategies, which the mining industry has to tailor for maximizing metal extractio