Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Sciences, ETH Zurich, CHN, CH-8092 Zurich, Switzerland.
Geochem Trans. 2009 Jun 13;10:5. doi: 10.1186/1467-4866-10-5.
Siderophore-promoted iron acquisition by microorganisms usually occurs in the presence of other organic molecules, including biosurfactants. We have investigated the influence of the anionic surfactant sodium dodecyl sulfate (SDS) on the adsorption of the siderophores DFOB (cationic) and DFOD (neutral) and the ligand EDTA (anionic) onto goethite (alpha-FeOOH) at pH 6. We also studied the adsorption of the corresponding 1:1 Fe(III)-ligand complexes, which are products of the dissolution process. Adsorption of the two free siderophores increased in a similar fashion with increasing SDS concentration, despite their difference in molecule charge. In contrast, SDS had little effect on the adsorption of EDTA. Adsorption of the Fe-DFOB and Fe-DFOD complexes also increased with increasing SDS concentrations, while adsorption of Fe-EDTA decreased. Our results suggest that hydrophobic interactions between adsorbed surfactants and siderophores are more important than electrostatic interactions. However, for strongly hydrophilic molecules, such as EDTA and its iron complex, the influence of SDS on their adsorption seems to depend on their tendency to form inner-sphere or outer-sphere surface complexes. Our results demonstrate that surfactants have a strong influence on the adsorption of siderophores to Fe oxides, which has important implications for siderophore-promoted dissolution of iron oxides and biological iron acquisition.
微生物通过铁载体促进铁的获取通常发生在存在其他有机分子的情况下，包括生物表面活性剂。我们研究了阴离子表面活性剂十二烷基硫酸钠（SDS）对铁载体 DFOB（阳离子）和 DFOD（中性）以及配体 EDTA（阴离子）在 pH 6 下在针铁矿（α-FeOOH）上吸附的影响。我们还研究了相应的 1:1 Fe(III)-配体络合物的吸附，它们是溶解过程的产物。尽管两种游离铁载体的分子电荷不同，但它们的吸附均随着 SDS 浓度的增加而以相似的方式增加。相比之下，SDS 对 EDTA 的吸附影响很小。Fe-DFOB 和 Fe-DFOD 配合物的吸附也随着 SDS 浓度的增加而增加，而 Fe-EDTA 的吸附则减少。我们的结果表明，吸附的表面活性剂之间的疏水相互作用比静电相互作用更重要。然而，对于强亲水分子，如 EDTA 和其铁配合物，SDS 对其吸附的影响似乎取决于它们形成内球或外球表面配合物的趋势。我们的结果表明，表面活性剂对铁载体在铁氧化物上的吸附有很强的影响，这对铁载体促进铁氧化物的溶解和生物铁的获取有重要意义。
