Control of catecholate siderophore metal preference by fulvic acid

铁载体是由微生物产生的有机分子，作为在铁胁迫条件下获取铁的一种手段，在许多土壤和沉积物中都存在。目前认为，这些分子对铁的亲和力和选择性高于土壤溶液中任何其他元素。由于土壤的复杂性和异质性，铁载体与许多其他成分一起出现，最著名的是富里酸，一种普遍存在的有机物质，具有相当的反应性和重要性。在我们的实验室中，我们已经证明，黄腐酸与肠杆菌形成密切的联系，肠杆菌是一种特征良好的铁载体，对铁具有非常高的亲和力。更重要的是，我们已经观察到，当黄腐酸与肠杆菌蛋白结合时，这种铁载体对铁的亲和力大大降低，同时对铬的亲和力增加。这种令人惊讶的金属偏好逆转在同时含有铁和铬的矿物的溶解过程中最为明显，在此过程中，铬比铁优先溶解。我们观察到的黄腐酸依赖性肠菌素金属偏好的变化有几个原因。首先，需要重新评估含有铁和铬的矿物的溶解速率和机制，以适应肠杆菌素和黄腐酸大量同时出现的环境。此外，根据其化学形态和浓度，铬既可以作为必需营养素，也可以作为毒素，因此黄腐酸-肠杆菌蛋白的存在可能影响该元素的相对可用性和毒性。这项工作的一个更广泛的含义涉及铁和铬的全球地球化学循环，可能还有其他元素，这部分取决于肠obactin和黄腐酸之间复杂的相互作用。此外，我们的研究结果可能为开发和设计无毒有效的治疗性螯合剂提供信息，这是目前药理学行业的许多工作的重点。本研究旨在发现黄腐酸在含铁和含铬矿物溶解过程中改变肠菌素金属偏好的程度和条件。为此，我们将开发模型，描述在黄腐酸-肠杆菌络合物存在下，铁和铬从一种常见的土壤矿物质中释放出来。

Siderophores are organic molecules produced by micro-organisms as a means to acquire iron under conditions of iron stress, as occurs in many soils and sediments. It is currently believed that these molecules have a higher affinity and selectivity for iron than for any other element in soil solution. As a consequence of the complexity and heterogeneity of soils, siderophores occur in association with many other constituents, most notably fulvic acid, a ubiquitous organic material of considerable reactivity and importance. In our laboratory we have shown that fulvic acid forms intimate associations with enterobactin, a well-characterized siderophore of remarkably high affinity for iron. More importantly, we have observed that when fulvic acid is bound to enterobactin, this siderophore displays much-reduced affinity for iron and a concomitant increase in affinity for chromium. This surprising reversal of metal preference is most apparent during the dissolution of minerals containing both iron and chromium, during which chromium is dissolved preferentially over iron. The fulvic acid-dependent change in enterobactin metal preference we observe is of interest for several reasons. First, the rates and mechanisms of dissolution of minerals containing both iron and chromium will need to be reassessed for environments in which enterobactin and fulvic acid occur together in significant quantities. Also, as chromium may serve as either an essential nutrient or as a toxin, depending on its chemical form and concentration, the presence of fulvic acid-enterobactin associations may influence the relative availability and toxicity of this element. A broader implication of this work concerns the global geochemical cycling of iron and chromium, and perhaps other elements, which depend in part on the complex interactions between enterobactin and fulvic acid. Furthermore, results of our investigations may inform development and design of non-toxic and effective therapeutic chelating agents, currently the focus of much work in the pharmacology industry. This research aims to discover the extent and conditions under which fulvic acid modifies enterobactin metal preference during dissolution of minerals containing both iron and chromium. To this end we will develop models describing iron and chromium release from a common soil mineral in the presence of fulvic acid-enterobactin complexes.