Adaptive mechanism of Acidithiobacillus thiooxidans CCTCC M 2012104 under stress during bioleaching of low-grade chalcopyrite based on physiological and comparative transcriptomic analysis.

Acidithiobacillus thiooxidans (A. thiooxidans) is often used for sulfur-bearing ores bioleaching, but its adaptive mechanism to harsh environments remains unclear. Here, we explored the adaptive mechanism of A. thiooxidans in the process of low-grade chalcopyrite bioleaching based on the physiology and comparative transcriptome analysis. It was indicated that A. thiooxidans maintains intracellular pH homeostasis by regulating unsaturated fatty acids, especially cyclopropane fatty acids, intracellular ATP, amino acid metabolism, and antioxidant factors. Comparative transcriptome analysis indicated that the key genes involved in sulfur oxidation, sor and soxABXYZ, were significantly up-regulated, generating more energy to resist extreme environmental stress by more active sulfur metabolism. Confocal laser scanning microscope analysis found that down-regulation of flagellar-related genes was likely to promote the biofilm formation. System-level understanding of leaching microorganisms under extreme stress can contribute to the evolution of these extremophiles via genetic engineering modification work, which further improves bioleaching in future.