Laboratory of Microbial Interactions, Department of Molecular and Cellular Interactions, Flanders Institute for Biotechnology (VIB), Vrije Universiteit Brussel, Building E, Pleinlaan 2, 1050 Brussels, Belgium. Université de Rouen, Laboratoire M2C, UMR CNRS 6143, groupe microbiologie, Bâtiment IRESE B, UFR des Sciences, 76821 Mont Saint Aignan, France.
Environ Microbiol Rep. 2009 Aug;1(4):256-62. doi: 10.1111/j.1758-2229.2009.00041.x. Epub 2009 Jun 22.
For bacteria with an aerobic lifestyle, iron is in the oxidized Fe(3+) form, hence poorly soluble. The solution is the synthesis and excretion of siderophores with a high affinity for iron. These ferrisiderophores are recognized by TonB-dependent outer membrane receptors in Gram-negative bacteria. Haem is also a source of iron and is captured via TonB-dependent receptors as well. In many cases bacterial genomes encode genes for receptors for siderophores produced by other microorganisms (xenosiderophores). Pseudomonads are known for their high adaptive capacity and it is therefore not surprising to find a relatively large number of genes encoding these receptors. In this study we analysed the genomes of three fluorescent pseudomonads available in the Pseudomonas genome database (http://www.pseudomonas.com; P. aeruginosa, P. putida, P. syringae) in order to extract the genes coding for TonB-dependent receptors. As expected we observed differences between species for the number of receptors. We also report differences within species, suggesting the acquisition of some genes via horizontal gene transfer, including those coding for the ferripyoverdine receptors. We also report cases where duplications of receptor genes are observed and the presence of 'receptor islands'. Our study strongly supports the notion of 'core' and 'accessory' TonB-dependent receptors within each species, with the ferripyoverdine receptors belonging to the last category.
对于需氧生活方式的细菌，铁呈氧化态的 Fe(3+)形式，因此溶解度较低。解决方法是合成和排泄与铁具有高亲和力的铁载体。这些亚铁载体被革兰氏阴性菌中的 TonB 依赖性外膜受体识别。血红素也是铁的来源，也通过 TonB 依赖性受体捕获。在许多情况下，细菌基因组编码用于捕获其他微生物（异源铁载体）产生的铁载体的受体基因。假单胞菌以其高适应能力而闻名，因此发现大量编码这些受体的基因并不奇怪。在这项研究中，我们分析了三个可在荧光假单胞菌基因组数据库（http://www.pseudomonas.com；铜绿假单胞菌、恶臭假单胞菌、丁香假单胞菌）中获得的荧光假单胞菌的基因组，以提取编码 TonB 依赖性受体的基因。正如预期的那样，我们观察到不同物种之间的受体数量存在差异。我们还报告了物种内的差异，表明通过水平基因转移获得了一些基因，包括编码 ferripyoverdine 受体的基因。我们还报告了观察到受体基因重复和存在“受体岛”的情况。我们的研究强烈支持每个物种内存在“核心”和“辅助”TonB 依赖性受体的观点，而 ferripyoverdine 受体属于后者。
