Reverse-transcription qualitative PCR(RT-qPCR)was used to analyze the changes in transcription levels of the sulfur metabolism-related periplasmic protein genes of Acidithiobacillus ferrooxidans ATCC 23270 grown on sulfur or ferrous.Seven periplasmic proteins with apparently higher abundance grown on elemental sulfur than on ferrous sulfate were identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF-MS).Expression analysis of the corresponding genes by RT-qPCR shows that the constitutive expression of all those genes are more up-regulated grown on sulfur than those grown on ferrous(>10 folder).Study on the corresponding genes of the identified periplasmic proteins by RT-qPCR confirmed the results of two-dimensioned gel electrophoresis,indicating they may be related with sulfur metabolism in A.ferrooxidans.
The differential utilization of cyclic, orthorhombic α-sulfur （α-S） and chain-like polymeric g-sulfur （μ-S） by Acidithiobacillus ferrooxidans was investigated. The growth and sulfur oxidation results indicated that utilization of μ-S by A. ferrooxidans was clearly different from α-S. Even if the planktonic cells were produced, the fall of pH and the rise of sulfate concentration were the same after 300 h on each substrate, the speeds of the planktonic cells increase, pH decrease and sulfate concentration increase in the earlier cultivation stage were faster on polymeric sulfur compared with the orthorhombic form. The adsorption capacity of the cells was higher on μ-S than on α-S, The results of SEM, DRIFTS and XRD analyses indicated that the surfaces of α-S and μ -S were modified differently by cells. Differential expression of 11 selected sulfur adsorption-activation and metabolism relevant genes was detected by RT-qPCR. The results showed that the expression of the hydrophobic substrate transport proteins and the sulfur metabolism related proteins was up-regulated, and the adsorption and activation related proteins were down-regulated when the cells were grown on μS, suggesting that μ-S could be more easily bio-adapted and activated than α-S.
The influence of initial pH on the chalcopyrite oxidation dissolution at 65 ℃ was investigated by bioleaching and cyclic voltammetiy experiments,and the oxidation products were investigated by XRD and Raman spectroscopy.Bioleaching results show that chalcopyrite dissolution rate increases with the decrease of the initial pH in chemical leaching,while the influence of initial pH on bioleaching is on the contrary.The presence of Acidianus manzaensis does not promote chalcopyrite dissolution under initial pH1.0,which mainly results from serious inhibition of high acidity to the growth of Acidianus manzaensis.Electrochemical experiments results show that anodic oxidation currents of electrolyte with or without Acidianus manzaensis both increase with the increase of initial pH,and covellite and sulfur are detected on the electrode surface.The results confirm that chalcopyrite dissolution in chemical leaching is under the combined action of oxidation and non-oxidation of proton,with conversion of chalcopyrite to covellite and elemental sulfur.
One bioleaching bacterium, named as strain DXS, was isolated from acid mine drainages （AMDs） of Dongxiangshan Mine of Hami, Xinjiang Province, China. The strain DXS is gram-negative and rod-shaped with a size of （0.40±0.05） μm x （1.3±0.5） μm. The optimal temperature and pH for growth are 30 ℃ and pH 2.0, respectively. It can grow autotrophically by using ferrous iron, elemental sulfur and NaS203 as sole energy sources. In the phylogenetic tree, strain DXS has similarity with Acidithiobacillus ferrooxidans type strain ATCC 23270 with 99.57% sequence similarity. The cloning and sequencing of Iro protein gene （iro） and tetrathionate hydrolase gene （tth） reveal that strain DXS is completely identical in iro gene sequence to A. ferrooxidans LY （DQ166841）, and almost identical in tth gene sequene to .4. ferrooxidans （AB259312） （only two nucleotides change）. The bioleaching experiments of marmatite and pyrite reveal that the leached zinc and iron concentrations reach 3.01 g/L and 2.75 g/L, respectively. The strain has a well potential application in industry bioleaching.
