Characterization of the acid stress response of Acidithiobacillus ferrooxidans ATCC 23270 based on the method of microarray

Bioleaching has become a research hotspot, as a simple and effective technology for metal extraction from low-grade ores. During the process of bioleaching, the chemoautotroph organisms play a key role. However, their growth and activity are greatly restrained by the stress brought by over acidic extracellular environment in industrial practice. This research effort focused on the transciptome profile discrepancies of the typical bioleaching species Acidithiobacillus ferrooxidans ATCC 23270 when challenged by a pH downshift to pH 1.2 using the method of microarray. A total of 1853 genes were found to be significantly affected under acid stress challenge for 1 hr, and the array data revealed that A. ferrooxidans ATCC 23270 actively responses to acid stress from several levels: cell envelope level, cytoplasm level and transcription level. One remarkable change is that the ion transporters and the synthesis of glutamine and polyamines were regulated in chemoautotrophic A. ferrooxidans ATCC 23270 under acid stress, while in contrast, typical heterotrophic bacteria Escherichia coli depended on up-regulation of ATP synthase F0F1 and glutamate decarboxylase system. More specifically, the alkaline substances generated by glnA, glnB, glnD, glnE etc. were functional in buffering the cytoplasm pH, and certain proton pumps such as cytoplasm protons plasma-membrane proton transport P-type ATPase played an important role in proton expulsion to keep cytoplasm pH in certain range. The new information provided in this study could lead to a better understanding of the acid resistance mechanisms exhibited by autotrophic acidophilic bacteria.