Thiol-Rich Proteins Play Important Role in Adhesion and Sulfur Oxidation Process of Acidithiobacillus ferroxidans

The proteomics of the extracellular proteins (EPs), outer membrane proteins (OMPs) and the periplasmic proteins (PPs) of Acidithiobacillus ferrooxidans ATCC 23270 grown on Fe2+ and S0 substrates, respectively, were comparatively studied. 39 expression up-regulated proteins (including 13 EPs, 9 OMPs and 17 PPs) were identified and 70% of them contain cysteine residues in sequence. Some of the selected proteins especially the EPs contain abundant of the cysteine residues and one or more-CXXC-functional motifs. The thiol groups on the At. ferrooxidans cell surface were selectively marked by Ca2+ and SR-μ-XRF mapping in situ observation revealed that the number of thiols on the surface of the cells grown on S0 was about five times as that grown on Fe2+ substrate. When 0.01 g/L surfactant Tween-80 was added in the S0 culture medium, the adsorption and activation related EPs were down-regulated and the sulfur metabolism related proteins was up-regulated. The same phenomenon was observed when the cells were grown on the more easily adhesion sulfur allotrope μ-S. It indicates that the thiol-rich proteins played important roles in adhesion and sulfur oxidation process of At. ferrooxidans.