Rio Tinto bacteria. Light microscopy footage of water from the Rio Tinto river in Spain. This river flows through an area rich in minerals, and contains extremophile bacteria that feed on iron and sulphide minerals, creating an acidic environment. Over many kilometres this river has a pH of 2 and the reddish tint for which it is named. This river carries many tonnes of minerals, such as zinc and copper, to the sea. Despite the toxic environment, this river contains many microbe and algae species that are adapted to survive in such conditions. The orange-red colour is due to dissolved minerals such as ferrous sulphate (iron [II] sulphate).