Abstract An isolate of Thiobacillus ferrooxidans derived from gold mine water samples was repeatedly subcultured at increasing temperatures (from 30° to 42°C) in 9K medium. The temperature-adapted strain was found to be more efficient in the bioleaching of pyrite mineral than the wild type. When temperature-tolerant strains were cultured repeatedly in 9K medium at 30°C, the temperature tolerance was completely lost. These results indicate that the temperature tolerance was stress-dependent and not a permanent trait of the adapted strain. The potential utility of such temperature-tolerant strains of Thiobacillus ferrooxidans in sulphide mineral dissolution is demonstrated.