嗜酸氧化亚铁硫杆菌表面双电层电势分布模拟

Numerical modeling of potential profiles in electrical double layer of Acidithiobacillus ferrooxidans cell surface

采用离子可透过模型和不可透过模型,通过数值拟合的方法计算嗜酸氧化亚铁硫杆菌的表面电荷密度、空间电荷密度、表面电位和道南电位等。Zeta电位测定结果表明：以硫为能源培养的细菌细胞等电点（IEP）高于报道的以亚铁培养的细菌的。运用表面基团离子化模型模拟实验数据得出：以硫培养的嗜酸氧化亚铁硫杆菌的IEP〉2,这主要是由细菌表面蛋白质的氨基电离引起的。采用离子可透过模型分析表明：pH〈5时,细菌表面电位（φ0）和道南电位（φDON）下降较快;细菌表面的pH值等于细胞内的pH（约6-7）后,细菌的φ0和φDon的变化渐缓;计算得到细菌表面的双电层的厚度约为5 nm。细菌表面的双电层将影响浸矿体系中离子迁移和营养物质传输,而细菌彼此表面双电层的相互作用对细菌聚集不利。

The surface charge density,space charge density,surface potential（φ0） and Donnan potential（φDon） on the surface of Acidithiobacillus ferrooxidans cultivated with elemental sulfur（S-A.ferrooxidans） were calculated by numerical simulation using the ion-impenetrable and ion-penetrable models.Zeta potential measurement show that the isoelectric point（IEP） of S-A.ferrooxidans is higher than that of bacterium cultured with Fe2＋.It is concluded from fitting data by ionizable surface group model that S-A.ferrooxidans surface probably consists of much proteins,the ionization of amino group of which causes higher IEP（2）.The ion-penetrable model reveals that φ0 and φDon decrease rapidly at pH5 but hardly change when pH is 6-7.The thickness of electrical double layer of S-A.ferrooxidans is estimated as 5 nm.The electrical double layer of bacterial cell surface may have significant implications for ions transfer and nutrient transport,but their interaction is unfavorable for bacterial aggration.