System-level understanding of the potential acid-tolerance components of Acidithiobacillus thiooxidans ZJJN-3 under extreme acid stress
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In previous study, two extremely acidophilic strains Acidithiobacillus thiooxidans ZJJN-3 (collection site: bioleaching leachate) and ZJJN-5 (collection site: bioleaching wastewater) were isolated from a typical industrial bio-heap in China. Here, we unraveled the potential acid-tolerance components of ZJJN-3 by comparing the physiological differences with ZJJN-5 under different acid stresses. The parameters used for comparison included intracellular pH (pHin), capsule morphology, fatty acid composition of cell membrane, transcription of key molecular chaperones, H+-ATPase activities and NAD+/NADH ratio. It was indicated that the acid-tolerance of A. thiooxidans ZJJN-3 was systematically regulated. Capsule first thickened and then shed off along with increased acid stress. Cell membrane maintained the intracellular stability by up-regulating the proportion of unsaturated fatty acid and cyclopropane fatty acids. Meanwhile, the transcription of key repair molecular chaperones (GrpE–DnaK–DnaJ) was up-regulated by 2.2–3.5 folds for ensuring the proper folding of peptide. Moreover, low pHin promoted ZJJN-3 to biosynthesize more H+-ATPase for pumping H+ out of cells. Furthermore, the NAD+/NADH ratio increased due to the decreased H+ concentration. Based on the above physiological analysis, the potential acid-tolerance components of A. thiooxidans ZJJN-3 were first proposed and it would be useful for better understanding how these extremophiles responded to the high acid stress.
KeywordsA.thiooxidans Extremophiles Acid-tolerance components Sulfuric acid
This work was supported by grants from the National Natural Science Foundation of China (Grant Nos. 31301540 and 21306064), the National High Technology Research and Development Program of China (863 Program) (Nos. 2012AA021201 and 2012AA021302), the Priority Academic Program Development of Jiangsu Higher Education Institutions, the 111 Project (No. 111-2-06), Natural Science Foundation of Jiangsu Province (No. BK20150133), and Scientific Program of Jiangnan University (No. JUSRP11538).
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