Ag significantly promoted the biofilm formation of thermoacidophilic archaeon Acidianus manzaensis YN-25 on chalcopyrite surface.

Silver ion (Ag) is an important catalyst to improve chalcopyrite bio-dissolution, but its effects on initial adhesion behaviors and biofilm formation of acidophiles onto metal sulfide were still unknown. In this study, initial attachment behavior and adhesion force in the presence of Ag (0, 1, 2, 5, 10 and 20 mg/L) were comparatively analyzed for Acidianus manzaensis YN-25. Biofilm was observed by fluorescent images in the presence of 0, 1 and 2 mg/L Ag. X-ray photoelectron spectroscopy (XPS) corroborated the catalytic mechanisms of Ag to biofilm formation. Results showed that Ag could significantly promote the attachment of cells on chalcopyrite, and the optimum concentration of Ag was 2 mg/L with the biggest percentage of attached cells (74%), followed by 5 mg/L (71%), whereas that for the control (0 mg/L) was only 61%. Ag significantly increased the interaction force between A. manzaensis YN-25 and chalcopyrite. Compared with the control, larger coverage of biofilm (up to 40% versus 32%) and more corrosion pits were observed on chalcopyrite in the presence of 2 mg/L Ag. Moreover, Ag catalyzed chalcopyrite corrosion and accelerated biofilm formation by producing a loose porous AgS layer and Ag to decrease the resistivity. The live/dead ratio was small with a range of 0.31-1.38, suggesting that dead cells were a great slice during the whole life-cycle of biofilm on chalcopyrite. This report offers a profound insight into the promotion mechanism of Ag on adhesion behaviors and biofilm formation by thermoacidophilic archaeon under extremely acidic conditions.