The σ54-dependent two-component system regulating sulfur oxidization (Sox) system in Acidithiobacillus caldus and some chemolithotrophic bacteria

• Published in: Applied microbiology and biotechnology 2017-03, Vol.101 (5), p.2079-2092
• Main Authors: Li, Li-Feng, Fu, Luo-Jie, Lin, Jian-Qun, Pang, Xin, Liu, Xiang-Mei, Wang, Rui, Wang, Zhao-Bao, Lin, Jian-Qiang, Chen, Lin-Xu
• Format: Article
• Language: English
• Subjects: Applied Genetics and Molecular Biotechnology; Biomedical and Life Sciences; Biotechnology; Life Sciences; Microbial Genetics and Genomics; Microbiology
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-016-8026-2

The s ulfur ox idization (Sox) system is the central sulfur oxidization pathway of phototrophic and chemotrophic sulfur-oxidizing bacteria. Regulation and function of the Sox system in the chemotrophic Paracoccus pantotrophus has been elucidated; however, to date, no information is available on the regulation of this system in the chemolithotrophic Acidithiobacillus caldus , which is widely utilized in bioleaching. We described the novel tspSR - sox -like clusters in A. caldus and other chemolithotrophic sulfur-oxidizing bacteria containing Sox systems. The highly homologous σ 54 -dependent two-component signaling system (TspS/R), upstream of the sox operons in these novel clusters, was identified by phylogenetic analyses. A typical σ 54 -dependent promoter, P 1 , was identified upstream of sox X-I in the sox -I cluster of A. caldus MTH-04. The transcriptional start site (G) and the −12/−24 regions (GC/GG) of P 1 were determined by rapid amplification of cDNA ends (5′RACE), and the upstream activator sequences (UASs; TGT CCCAAATGGG ACA ) were confirmed by electrophoretic mobility shift assays (EMSAs) in vitro and by UAS-probe-plasmids assays in vivo. Sequence analysis of promoter regions in tspSR - sox -like clusters revealed that there were similar σ 54 -dependent promoters upstream of the soxX genes. Based on our results, we proposed a TspSR-mediated signal transduction and transcriptional regulation pathway for the Sox system in A. caldus . The regulation of σ 54 -dependent two-component systems (TCSs) for Sox pathways were explained for the first time in A. caldus , A. thiooxidans , T. tepidarius , and T. denitrificans , indicating the significance of modulating the sulfur oxidization in these chemolithotrophic sulfur oxidizers.