Ferric iron uptake genes are differentially expressed in the presence of copper sulfides in Acidithiobacillusferrooxidans strain LR

• Published in: Antonie van Leeuwenhoek Vol. 99; no. 3; pp. 609 - 617
• Main Authors: Ferraz, Lúcio F. C., Verde, Leandro C. L., Vicentini, Renato, Felício, Ana P., Ribeiro, Marcelo L., Alexandrino, Fabiana, Novo, Maria T. M., Garcia, Oswaldo, Rigden, Daniel J., Ottoboni, Laura M. M.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 2011
• Subjects: Biomedical and Life Sciences; Life Sciences; Medical Microbiology; Microbiology; Original Paper; Plant Sciences; Soil Science & Conservation; Siderophore-mediated Fe(III) uptake genes; Copper sulfides
• ISSN: 0003-6072; 1572-9699
• DOI: 10.1007/s10482-010-9533-2

Acidithiobacillus ferrooxidans
is one of the most widely used microorganisms in bioleaching operations to recover copper from low-grade copper sulfide ores. This work aimed to investigate the relative expression of genes related to the iron uptake system when
A. ferrooxidans
LR was maintained in contact with chalcopyrite or bornite as the sole energy source. Real-time quantitative PCR analysis revealed that the presence of bornite had no effect on the expression of seven genes related to the siderophore-mediated Fe(III) uptake system, while in the presence of chalcopyrite the expression of the genes was up-regulated. Bioinformatic analysis of the genomic region where these genes were found revealed the existence of three new putative DNA-binding sequences for the ferric iron uptake transcriptional regulator (Fur). Electrophoretic mobility shift assays demonstrated that a purified
A. ferrooxidans
His-tagged Fur protein was able to bind in vitro to each of these putative Fur boxes, suggesting that Fur regulated the expression of these genes. The expression of
fur
and two known Fur-regulated genes,
mntH
and
dsrK
, was also investigated in the presence of chalcopyrite. While the expression of
fur
and
mntH
was up-regulated, the expression of
dsrK
was down-regulated. The low amount of ferrous iron in the medium was probably responsible for the up-regulation of
fur
and the genes related to the siderophore-mediated Fe(III) uptake system when
A. ferrooxidans
LR was kept in the presence of chalcopyrite. A homology model of the
A.
ferrooxidans
Fur was constructed and revealed that the putative DNA-binding surface presents conserved positively charged residues, supporting a previously suggested mode of interaction with DNA. The up-regulation of
fur
and the siderophore-mediated Fe(III) uptake genes, and the down-regulation of
dsrK
suggest that in the presence of chalcopyrite Fur acts as a transcription inducer and repressor.