Open AccessDiscovery of a new subgroup of sulfur dioxygenases and characterization of sulfur dioxygenases in the sulfur metabolic network of Acidithiobacillus caldus
Author(s) -
Wei Wu,
Xin Pang,
Jianqiang Lin,
Xiangmei Liu,
Rui Wang,
Linxu Chen
Publication year - 2017
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0183668
Subject(s) - sulfur , sulfur metabolism , acidithiobacillus ferrooxidans , acidithiobacillus , chemistry , acidithiobacillus thiooxidans , biology , biochemistry , bioleaching , organic chemistry , copper
Acidithiobacillus caldus is a chemolithoautotrophic sulfur-oxidizing bacterium that is widely used for bioleaching processes. Acidithiobacillus spp. are suggested to contain sulfur dioxygenases (SDOs) that facilitate sulfur oxidation. In this study, two putative sdo genes (A5904_0421 and A5904_1112) were detected in the genome of A . caldus MTH-04 by BLASTP searching with the previously identified SDO (A5904_0790). We cloned and expressed these genes, and detected the SDO activity of recombinant protein A5904_0421 by a GSH-dependent in vitro assay. Phylogenetic analysis indicated that A5904_0421and its homologous SDOs, mainly found in autotrophic bacteria, were distantly related to known SDOs and were categorized as a new subgroup of SDOs. The potential functions of genes A5904_0421 (termed sdo1 ) and A5904_0790 (termed sdo2 ) were investigated by generating three knockout mutants (Δ sdo1 , Δ sdo 2 and Δ sdo1&2 ), two sdo overexpression strains (OE- sdo1 and OE- sdo2 ) and two sdo complemented strains (Δ sdo1/sdo1 ’ and Δ sdo2/sdo2 ’) of A . caldus MTH-04. Deletion or overexpression of the sdo genes did not obviously affect growth of the bacteria on S 0 , indicating that the SDOs did not play an essential role in the oxidation of extracellular elemental sulfur in A . caldus . The deletion of sdo1 resulted in complete inhibition of growth on tetrathionate, slight inhibition of growth on thiosulfate and increased GSH-dependent sulfur oxidation activity on S 0 . Transcriptional analysis revealed a strong correlation between sdo1 and the tetrathionate intermediate pathway. The deletion of sdo2 promoted bacterial growth on tetrathionate and thiosulfate, and overexpression of sdo2 altered gene expression patterns of sulfide:quinone oxidoreductase and rhodanese. Taken together, the results suggest that sdo1 is essential for the survival of A . caldus when tetrathionate is used as the sole energy resource, and sdo2 may also play a role in sulfur metabolism.