An extended siderophore suite from Synechococcus sp. PCC 7002 revealed by LC-ICPMS-ESIMS
An extended siderophore suite from Synechococcus sp. PCC 7002 revealed by LC-ICPMS-ESIMS
Date
2015-03-11
Authors
Boiteau, Rene M.
Repeta, Daniel J.
Repeta, Daniel J.
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Abstract
Siderophores are thought to play an important role in iron cycling in the ocean, but
relatively few marine siderophores have been identified. Sensitive, high throughput
methods hold promise for expediting the discovery and characterization of new
siderophores produced by marine microbes. We developed a methodology for
siderophore characterization that combines liquid chromatography (LC) inductively
coupled plasma mass spectrometry (ICPMS) with high resolution electrospray ionization
mass spectrometry (ESIMS). To demonstrate this approach, we investigated siderophore
production by the marine cyanobacteria Synechococcus sp. PCC 7002. Three
hydroxamate siderophores, synechobactin A-C, have been previously isolated and
characterized from this strain. These compounds consist of an iron binding head group
attached to a fatty acid side chain of variable length (C12, C10, and C8 respectively). In
this study, we detected six iron-containing compounds in Synechococcus sp. PCC 7002
media by LC-ICPMS. To identify the molecular ions of these siderophores, we aligned
the chromatographic retention times of peaks from the LC-ICPMS chromatogram with
features detected from LC-ESIMS spectra using an algorithm designed to recognize
metal isotope patterns. Three of these compounds corresponded to synechobactins A
(614 m/z), B (586m/z), and C (558m/z). The MS2 spectra of these compounds revealed
diagnostic synechobactin fragmentation patterns which were used to confirm the identity
of the three unknown compounds (600, 628, and 642 m/z) as new members of the
synechobactin suite with side chain lengths of 11, 13, and 14 carbons. These results
demonstrate the potential of combined LCMS techniques for the identification of novel
iron-organic complexes.
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Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Royal Society of Chemistry for personal use, not for redistribution. The definitive version was published in Metallomics 7 (2015): 877-884, doi:10.1039/C5MT00005J.