Strand-specific RNA-seq analysis of the Acidithiobacillus ferrooxidans transcriptome in response to magnesium stress

Deping Tang, Jiangong Duan, Qiyu Gao, Yang Zhao, Yang Li, Peng Chen, Jianping Zhou, Zhengrong Wu, Ruixiang Xu, Hongyu Li

Bioleaching is a promising process for 350 million tons Jinchuan low-grade pentlandite. But, Jinchuan pentlandite has lots of magnesium and high concentration of Mg2+ is harmful to bioleaching microorganisms. Thus, finding a way to improve the adaption of microorganisms to Mg2+ is a key for bioleaching. In the study, we found that oxidizing activity, bioleaching ability and biofilm formation of A.f were inhibited by Mg2+ stress. In addition, we analyzed mRNA and small RNA (sRNA) of Acidithiobacillus ferrooxidans (A.f) under Mg2+ stress by strand-specific RNA-sequencing (ssRNA-seq). After the bioinformatics process, 2475 coding genes were obtained, and there were 33 differential expression genes (DEGs) in 0.1 M-VS-Con, including 28 down-regulated and 5 up-regulated, whereas 52 DEGs were obtained in 0.5 M-VS-Con, including 28 down-regulated and 24 up-regulated. Gene ontology analysis showed most of DEGs were involved in catalytic activity, metabolic process and single-organism process. Furthermore, we identified 636 sRNA and some differential expression sRNA that may respond to Mg2+ stress. Further analysis of DEGs suggested that Mg2+ stress reduced biofilm formation perhaps through inhibiting Type IV Pili-related gene expression and inhibited bacterial activity perhaps through affecting carbon fixation. The study provided the foundation to understand the mechanisms of Mg2+ resistance in A.f and may be helpful to improve bioleaching ability for pentlandit.