The importance of siderophores in iron nutrition of heterotrophic marine bacteria
The importance of siderophores in iron nutrition of heterotrophic marine bacteria
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DOI：
10.4319/lo.1999.44.3.0541
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发表时间：
1999-05-01
影响因子：
4.5
通讯作者：
Price, NM
中科院分区：
文献类型：
--
作者：
Granger, J;Price, NM
最近的研究表明，海水中溶解的铁与强有机配合物结合，具有与微生物铁螯合物相当的稳定常数。我们研究了七种异养海洋细菌从一些铁载体-铁复合物中获取铁的情况，包括去铁胺B （DFB）和部分从铁限制培养中纯化的海洋铁载体。在四株菌株的上清液中检测到羟肟酸铁载体，其中一株也产生儿茶酚。所有菌株都将铁结合到铁载体上，而不管它们是否自己产生铁载体，并且大多数菌株都将铁结合到DFB上。铁载体的吸收速率在铁限制菌株和配体之间相似。通过铁限制，海王星菌株对FeDFB的转运能力提高了20倍，而对未螯合铁（Fe'）的摄取在最高浓度时没有饱和，也不受细胞铁营养状况的调节。海王星吸收FeDFB的半饱和常数为15 nM，是所有微生物中报道的最低的铁铁载体。产生儿茶酚的菌株LMG1对铁的吸收在两个方面与其他菌株明显不同：LMG1不能吸收与DFB结合的铁；此外，铁限制的LMG1转运铁的速度比其他菌株快10倍，比铁充足的细胞上调46倍。实验证据表明，LMG1的铁转运可能是由表面相关的儿茶酚铁载体介导的，儿茶酚铁载体清除无机铁以及与较弱配合物结合的铁，如EDTA（乙二胺四乙酸）。该研究的综合结果突出了铁载体在异养海洋细菌铁运输中的重要性，并提示，通过推断，细菌可能依赖铁载体在原位获取铁。
Recent studies demonstrate that dissolved iron in seawater is bound to strong organic complexes that have stability constants comparable to those of microbial iron chelates. We examined iron acquisition by seven strains of heterotrophic marine bacteria from a number of siderophore-iron complexes, including desferrioxamine B (DFB) and marine siderophores partially purified from iron-limited cultures. Hydroxamate siderophores were detected in the supernatants of four strains, one of which also produced a catechol. All strains transported iron bound to siderophores regardless of whether or not they produced their own, and the majority took up iron bound to DFB. Uptake rates of Fe siderophores were similar among iron-limited strains and among ligands. Transport of FeDFB by strain Neptune was enhanced 20 times by iron limitation, whereas uptake of unchelated iron (Fe') did not saturate at the highest concentration tested and was not regulated by the iron nutritional status of the cells. The half-saturation constant for uptake of FeDFB by Neptune was 15 nM, the lowest reported for an Fe siderophore in any microorganism. Iron uptake by the catechol-producing strain, LMG1, differed markedly in two respects from the other strains: LMG1 could not take up iron bound to DFB; furthermore, transport of Fe' by iron-limited LMG1 was 10 times faster than the other strains and was upregulated 46 times compared to Fe-sufficient cells. Experimental evidence suggests that iron transport by LMG1 may be mediated by surface-associated catechol siderophores that scavenge inorganic ferric species as well as iron bound to weaker complexes, such as EDTA (ethylenediaminetetraacetic acid). The combined results of the study highlight the importance of siderophores in iron transport by heterotrophic marine bacteria and suggest, by inference, that bacteria may rely on siderophores to acquire iron in situ.