Doong Ruey-An, Schink Bernhard
Department of Nuclear Science, National Tsing Hua University, Hsinchu, Taiwan.
Environ Sci Technol. 2002 Jul 1;36(13):2939-45. doi: 10.1021/es0102235.
The reductive dissolution of poorly crystalline ferric oxides in the presence of cysteine was investigated to evaluate the potential of cysteine as a possible electron carrier to stimulate the reduction of iron(III) oxides by Geobacter sulfurreducens. The extent and rate of biotic and abiotic reduction of iron(III) oxides in the presence of cysteine at various concentrations were compared. Iron(III) oxides were reduced abiotically by cysteine. The initial rate and extent of iron(III) oxide reduction were correlated linearly with the cysteine concentration ranging from 0 to 6 mM. Also, addition of 0.5-2 mM cysteine significantly stimulated the rate and the extent of iron(III) oxide reduction in cultures of G. sulfurreducens. The cysteine concentration decreased in accordance with the increase of Fe(II) concentration and reached a nearly constant residual concentration. Cysteine depletion followed first-order kinetics and increased linearly with the cysteine concentration. An 8- to 11-fold increase in the extent of iron(III) oxide reduction relative to the abiotic system was observed. Comparison of sorbed and dissolved Fe(II) concentrations between cultures amended with cysteine and with other organic chelators showed that solubilization is not the main factor in cysteine-stimulated Fe(III) reduction. Addition of cystine could enhanced the extent of iron(III) oxide reduction, concomitant with the increase of the regenerated cysteine concentration and support the hypothesis that cysteine could serve as an electron carrier to transfer electrons from G. sulfurreducens to poorly crystalline iron(III) oxides.
研究了在半胱氨酸存在下结晶性较差的三价铁氧化物的还原溶解情况，以评估半胱氨酸作为可能的电子载体来刺激嗜硫产甲烷菌还原三价铁氧化物的潜力。比较了在不同浓度半胱氨酸存在下三价铁氧化物的生物还原和非生物还原的程度及速率。半胱氨酸可非生物还原三价铁氧化物。三价铁氧化物还原的初始速率和程度与0至6 mM的半胱氨酸浓度呈线性相关。此外，添加0.5 - 2 mM半胱氨酸可显著刺激嗜硫产甲烷菌培养物中三价铁氧化物的还原速率和程度。半胱氨酸浓度随Fe(II)浓度的增加而降低，并达到接近恒定的残留浓度。半胱氨酸的消耗遵循一级动力学，且随半胱氨酸浓度线性增加。相对于非生物体系，观察到三价铁氧化物还原程度增加了8至11倍。比较添加半胱氨酸和其他有机螯合剂的培养物中吸附态和溶解态Fe(II)的浓度表明，溶解作用不是半胱氨酸刺激Fe(III)还原的主要因素。添加胱氨酸可提高三价铁氧化物的还原程度，同时再生半胱氨酸浓度增加，支持了半胱氨酸可作为电子载体将电子从嗜硫产甲烷菌转移至结晶性较差的三价铁氧化物的假说。
