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.
Effects of two typical surfactants, Tween-80 and sodium isobutyl-xanthate (NaIBX), with different concentrations on the growth and sulfur-oxidizing activities of a new strain Acidithiobacillus albertensis BY-05, an acidophilic sulfur-oxidizing bacterium, were investigated. The results indicate that both surfactants can enhance the growth and sulfur-oxidizing activities of A. albertensis BY-05 only at some special concentrations, e.g., 10-4-10-8 g/L for NaIBX and lower than 10-8 g/L for Tween-80, but were inhibited and even harmful at higher concentrations. Both surfactants can not be metabolized by A. albertensis BY-05. The contact between the bacteria and the sulfur particles may be dependent upon both the extracellular substance and the surfactants, both of which provide the amphiphilic environment improving the attachment for bacteria to the sulfur particles surface. These data could be significant for enlarging the applications of both A. albertensis BY-05 and some typical surfactants for industrial bioleaching of sulfides minerals.
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.
A new strain named YTW315 was isolated from Dexing area using the double-layer culture technique. The morphological, biochemical and physiological characteristics of YTW315 were studied. Physiological investigation indicates that the strain YTW315 is a strict (obligate) chemolithoautotroph, metabolizing ferrous iron and pyrite. The optimal growth conditions for the strain are 40 ℃ and pH 1.6. A phylogenetic analysis based on 16S rRNA sequences shows that the isolate is clustered to Leptospirillum ferriphilum with 99.8% similarity to Leptospirillum ferriphilum strain Fairview and ATCC 49881. The molar fraction of DNA (G+C) of the isolate is 58.1%. The strain can tolerate high concentration of Fe(Ⅲ) and As(V) (500 mmol/L and 50 mmol/L, respectively). Bioleaching experiment indicates that the strain can oxidize Fe(Ⅱ) efficiently, and after 30 d, 44.56% of copper and 95.31% of iron are extracted from chalcopyrite and pyrite, respectively.
A new bacterial strain,was designated as strain Acidiphilium cryptum DX1-1,accumulates intracellular poly-β-hydroxybutyrate particles,four methods which have advantages and disadvantages for each were employed to extract PHB.Chloroform-sodium hypochlorite method is the best in extracting PHB form Acidiphilium cryptum DX1-1.The extraction rate reaches 73%,the purification rate is 92% and molecular weight is 326 kg/mol.Then the PHB extracted by this method was analyzed by ultraviolet-visible absorption spectroscopy,fourier transform infrared（FT-IR） and nuclear magnetic resonance（NMR）.The results show that PHB from strain DX1-1 has the same biochemical structure and character with PHB standard.Mass spectrometer（MS） analysis reveals that the long chain of PHB is destroyed when treated by chloroform-sodium hypochlorite.The differential scanning calorimetry（DSC） of PHB shows PHB from Acidiphilium cryptum DX1-1 has low degree of crystallinity which makes the PHB has a wider range of applications.
