Zinc Exploitation by Pathogenic Fungi

The ability of pathogenic microorganisms to assimilate nutrients from their host environment is one of the most fundamental aspects of infection. To counteract this, hosts attempt to withhold essential micro-nutrients from potentially harmful microbes to limit, or even prevent, their growth. This process is called nutritional immunity. For example, vertebrates, such as humans, express several iron-binding molecules to maintain extremely low free levels of this metal in the body. To overcome this restriction, successful pathogens have evolved sophisticated mechanisms to assimilate iron. These include high affinity transporters, siderophores, and transferrin-, ferritin-, and haem-binding proteins [1,2]. Indeed, iron acquisition is considered a vital virulence factor for many pathogens. However, nutritional immunity does not begin and end with iron. Vertebrates have also developed mechanisms to sequester other essential metals, such as zinc [3,4]. The importance of zinc sequestration and the strategies that successful pathogens employ to overcome this has only recently been realized.