The resilience and versatility of acidophiles that contribute to the bio-assisted extraction of metals from mineral sulphides

In this paper, a brief outline is presented on acidic ferric ion oxidation of mineral sulphides for the extraction of metals in both stirred tank reactors for mineral concentrates and heaps for low-grade ores. The identities and capabilities of the relatively few acidophiles that assist the oxidative processes are summarized and their responses to selected extremes in their growth environments described. Individually, the organisms adapt to the presence of high concentrations of heavy metals and other elements in the bioleaching environment, tolerate a wide range of acidities and can recover from prolonged exposure to temperatures significantly above their preferred temperatures for growth. However, the presence of chloride in their acidic environment presents a significant physiological challenge. Species that exhibit a chemotactic response and attachment to sulphide surfaces, where they can create their own micro-environments, would be favoured in both heap bioreactors with low availability of energy substrates and physically aggressive, agitated continuous stirred-tank reactor environments treating concentrates.