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Siderophores: Sending Out Shuttles to Scout for Iron

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Schematic Representation of a Siderophore Before and After Iron Acquisition. Siderophores: Sending out Shuttles to Scout for Iron. [Adapted from H. Boukhalfa and A. L. Crumbliss, “Chemical Aspects of Siderophore-Mediated Iron Transport,” Biometals 15, 25–39 (2002).] Another efficient mechanism evolved by many microbes to obtain iron in limited environments such as marine surfaces is the production and secretion of siderophores. These low-molecular-weight chelating agents act as shuttles to bind insoluble iron [Fe(III)] and transport it back to the microbe, where it enters the cell by recognizing specific membrane receptor proteins and transport systems. More than 500 types of siderophores are known to exist. In addition to supplying essential nutrients, siderophores of one organism can lock up iron to achieve an advantage over their competitors. However, some microbes were discovered recently to have receptors for the siderophores of other organisms. Until the genetic sequence of the ocean diatom T. pseudonana was determined in the DOE Microbial Genome Program and compared with sequences of other organisms, researchers were unaware that these organisms possessed siderophores. Diatoms, along with other ocean microbes, contribute to absorbing CO2 in amounts comparable to that absorbed by all the world’s tropical rain forests combined. Obtaining more detailed knowledge of their life processes will help us better understand their vital role in global carbon cycling. [Reference: E. V. Armbrust et al., “The Genome of the Diatom Thalassiosira pseudonana: Ecology, Evolution, and Metabolism,” Science 306, 79–86 (2004).]

Credit or Source: Genome Management Information System, Oak Ridge National Laboratory


US DOE. 2005. Genomics:GTL Roadmap, DOE/SC-0090, U.S. Department of Energy Office of Science. (p. 17) (website)

Prepared by the Biological and Environmental Research Information System, Oak Ridge National Laboratory, and