Molecular Determination of Marine Iron Ligands by Mass Spectrometry

Rene Boiteau, Ph.D., 2016
Dan Repeta, Advisor

Marine microbes produce a wide variety of metal binding organic ligands that regulate the solubility and uptake of biologically important metals such as iron, copper, cobalt, and zinc. In marine environments where the availability of iron limits microbial growth and carbon fixation rates, the ability to access organically bound iron confers a competitive advantage. Thus, the compounds that microbes produced to acquire iron play an important role in biogeochemical carbon and metal cycling. However, the source, abundance, and identity of these compounds are poorly understood. To investigate these processes, sensitive methodologies were developed to gain a compound-specific window into marine iron speciation using liquid chromatography hyphenated with inductively coupled plasma mass spectrometry and electrospray ionization mass spectrometry. These techniques were used to investigate the distribution and diversity of marine iron binding ligands. In cultures, new members of siderophore classes produced by marine microbes were identified. In samples collected across the Pacific Ocean, a wide diversity of both known and novel siderophores were identified. These siderophores reflect adaptations to specific ecological niches and have important consequences for dissolved iron bioavailability. These findings have opened new opportunities to better understand mechanisms that link metals with the microbes that use them.