Physiological diversity amongst some moderately thermophilic iron-oxidising bacteria

Abstract Three strains of moderately thermophilic and acidophilic bacteria capable of oxidising ferrous iron, isolated from different sources, were compared with each other and with an earlier isolate, TH1. The isolates displayed different rates of carbon dioxide fixation and incorporation of glucose and glycine; only one could be subcultured continuously in organic-free ferrous sulfate medium. Two of the isolates readily oxidised elemental sulfur, and all were capable of solubilising pyrite and chalcopyrite, though at different rates; there was no correlation between rates of ferrous iron and pyrite oxidation. Reduction of ferric iron by two of the isolates was observed in unshaken cultures containing 10 mM glucose. The DNA base composition of the isolates varied from 43–68 mol% G + C.