Boiteau Rene M, Repeta Daniel J
Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
Metallomics. 2015 May;7(5):877-84. doi: 10.1039/c5mt00005j. Epub 2015 Mar 18.
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 (586 m/z), and C (558 m/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.
铁载体被认为在海洋中的铁循环中发挥着重要作用，但已鉴定出的海洋铁载体相对较少。灵敏的高通量方法有望加快对海洋微生物产生的新铁载体的发现和表征。我们开发了一种铁载体表征方法，该方法将液相色谱（LC）电感耦合等离子体质谱（ICPMS）与高分辨率电喷雾电离质谱（ESIMS）相结合。为了证明这种方法，我们研究了海洋蓝细菌聚球藻属PCC 7002产生铁载体的情况。此前已从该菌株中分离并表征了三种异羟肟酸铁载体，即聚球藻素A - C。这些化合物由一个与可变长度脂肪酸侧链相连的铁结合头基组成（分别为C12、C10和C8）。在本研究中，我们通过LC - ICPMS在聚球藻属PCC 7002培养基中检测到六种含铁化合物。为了鉴定这些铁载体的分子离子，我们使用一种旨在识别金属同位素模式的算法，将LC - ICPMS色谱图中峰的色谱保留时间与LC - ESIMS光谱中检测到的特征进行比对。其中三种化合物对应于聚球藻素A（614 m/z）、B（586 m/z）和C（558 m/z）。这些化合物的MS2光谱揭示了诊断性的聚球藻素裂解模式，用于确认三种未知化合物（600、628和642 m/z）是聚球藻素家族的新成员，其侧链长度分别为11、13和14个碳。这些结果证明了联用LCMS技术在鉴定新型铁 - 有机复合物方面的潜力。
