Division of Environmental and Biomolecular Systems, Institute of Environmental Health, Oregon Health & Science University Portland, OR, USA.
Geosciences Research Division, Scripps Institution of Oceanography, University of California, San Diego San Diego, CA, USA.
Front Microbiol. 2014 Jun 25;5:301. doi: 10.3389/fmicb.2014.00301. eCollection 2014.
Pseudomonas putida GB-1 is a Mn(II)-oxidizing bacterium that produces pyoverdine-type siderophores (PVDs), which facilitate the uptake of Fe(III) but also influence MnO2 formation. Recently, a non-ribosomal peptide synthetase mutant that does not synthesize PVD was described. Here we identified a gene encoding the PVDGB-1 (PVD produced by strain GB-1) uptake receptor (PputGB1_4082) of strain GB-1 and confirmed its function by in-frame mutagenesis. Growth and other physiological responses of these two mutants and of wild type were compared during cultivation in the presence of three chemically distinct sets of PVDs (siderotypes n°1, n°2, and n°4) derived from various pseudomonads. Under iron-limiting conditions, Fe(III) complexes of various siderotype n°1 PVDs (including PVDGB-1) allowed growth of wild type and the synthetase mutant, but not the receptor mutant, confirming that iron uptake with any tested siderotype n°1 PVD depended on PputGB1_4082. Fe(III) complexes of a siderotype n°2 PVD were not utilized by any strain and strongly induced PVD synthesis. In contrast, Fe(III) complexes of siderotype n°4 PVDs promoted the growth of all three strains and did not induce PVD synthesis by the wild type, implying these complexes were utilized for iron uptake independent of PputGB1_4082. These differing properties of the three PVD types provided a way to differentiate between effects on MnO2 formation that resulted from iron limitation and others that required participation of the PVDGB-1 receptor. Specifically, MnO2 production was inhibited by siderotype n°1 but not n°4 PVDs indicating PVD synthesis or PputGB1_4082 involvement rather than iron-limitation caused the inhibition. In contrast, iron limitation was sufficient to explain the inhibition of Mn(II) oxidation by siderotype n°2 PVDs. Collectively, our results provide insight into how competition for iron via siderophores influences growth, iron nutrition and MnO2 formation in more complex environmental systems.
铜绿假单胞菌 GB-1 是一种锰(II)氧化细菌，它产生绿脓菌素型铁载体 (PVDs)，这有利于铁(III)的摄取，但也影响 MnO2 的形成。最近，描述了一种不能合成 PVD 的非核糖体肽合成酶突变体。在这里，我们鉴定了编码菌株 GB-1 中 PVDGB-1（由菌株 GB-1 产生的 PVD）摄取受体 (PputGB1_4082) 的基因，并通过框内诱变证实了其功能。在存在三种不同的 PVD（来自不同假单胞菌的 siderotype n°1、n°2 和 n°4）的情况下，比较了这两种突变体和野生型在培养过程中的生长和其他生理反应。在铁限制条件下，各种 siderotype n°1 PVD（包括 PVDGB-1）的 Fe(III) 配合物允许野生型和合成酶突变体生长，但不允许受体突变体生长，这证实了任何测试的 siderotype n°1 PVD 的铁摄取都依赖于 PputGB1_4082。siderotype n°2 PVD 的 Fe(III) 配合物不能被任何菌株利用，并强烈诱导 PVD 合成。相比之下，siderotype n°4 PVDs 的 Fe(III) 配合物促进了所有三种菌株的生长，并且不诱导野生型 PVD 合成，这意味着这些配合物被用于铁摄取，而不依赖于 PputGB1_4082。这三种 PVD 类型的不同性质提供了一种方法，可以区分由铁限制引起的 MnO2 形成的影响和需要 PVDGB-1 受体参与的影响。具体来说，siderotype n°1 但不是 n°4 PVD 抑制了 MnO2 的产生，这表明 PVD 合成或 PputGB1_4082 的参与而不是铁限制导致了抑制。相反，铁限制足以解释 siderotype n°2 PVD 对 Mn(II)氧化的抑制。总的来说，我们的研究结果提供了有关铁载体竞争如何影响更复杂环境系统中的生长、铁营养和 MnO2 形成的深入了解。
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