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Leptospirillum ferriphilum YXW was isolated through serial dilution from mixed microorganisms enriched in AMD from Dexing copper mine in Jiangxi Province, China. It was mutated by ultrasonic, UV and microwave methods to collect a more efficient strain for bioleaching of gold ore. Physiological and biochemical characteristics indicate that YXW is a strict chemoautotrophic microorganism, and the optimal condition for its growth occurs at 40 degrees C and pH 1.5. After mutation by ultrasonic, UV and microwave, the density of bacterial cells increased by 291%, 265% and 87%, respectively, compared with the original culture. The bacterial total protein activity was improved by microwave and UV mutations, but was reduced by ultrasonic. Mutations had effects on bioleaching of gold ore in sequence of microwave, UV, then ultrasonic. During gold ore bioleaching, the bacteria obtained after mutation by microwave had the best effect on the extraction rates of arsenic and iron, which were 19.6% and 17.7% higher than that of the original strain after bioleaching for 10 days. The results suggested that the effects of mutation on bioleaching of gold ore may not be mainly due to increase of bacterial cells density, but may be attributed to the improvement of bacterial total protein activity., Leptospirillum ferriphilum YXW was isolated through serial dilution from mixed microorganisms enriched in AMD from Dexing copper mine in Jiangxi Province, China. It was mutated by ultrasonic, UV and microwave methods to collect a more efficient strain for bioleaching of gold ore. Physiological and biochemical characteristics indicate that YXW is a strict chemoautotrophic microorganism, and the optimal condition for its growth occurs at 40 degrees C and pH 1.5. After mutation by ultrasonic, UV and microwave, the density of bacterial cells increased by 291%, 265% and 87%, respectively, compared with the original culture. The bacterial total protein activity was improved by microwave and UV mutations, but was reduced by ultrasonic. Mutations had effects on bioleaching of gold ore in sequence of microwave, UV, then ultrasonic. During gold ore bioleaching, the bacteria obtained after mutation by microwave had the best effect on the extraction rates of arsenic and iron, which were 19.6% and 17.7% higher than that of the original strain after bioleaching for 10 days. The results suggested that the effects of mutation on bioleaching of gold ore may not be mainly due to increase of bacterial cells density, but may be attributed to the improvement of bacterial total protein activity.