Estructura de Investigación Interdisciplinar en Biotecnología y Medicina (ERI BIOTECMED), Department of Microbiology and Ecology, University of Valencia, Dr. Moliner, 50, Valencia, 46100, Spain.
Department of Microbiology and Immunology, Institute of Basic Medical Sciences, Tainan, 701, Taiwan.
Environ Microbiol. 2015 Jun;17(6):2076-89. doi: 10.1111/1462-2920.12782. Epub 2015 Mar 4.
Vibrio vulnificus is a marine bacterium associated with human and fish (mainly farmed eels) diseases globally known as vibriosis. The ability to infect and overcome eel innate immunity relies on a virulence plasmid (pVvbt2) specific for biotype 2 (Bt2) strains. In the present study, we demonstrated that pVvbt2 encodes a host-specific iron acquisition system that depends on an outer membrane receptor for eel transferrin called Vep20. The inactivation of vep20 did not affect either bacterial growth in human plasma or virulence for mice, while bacterial growth in eel blood/plasma was abolished and virulence for eels was significantly impaired. Furthermore, vep20 is an iron-regulated gene overexpressed in eel blood during artificially induced vibriosis both in vitro and in vivo. Interestingly, homologues to vep20 were identified in the transferable plasmids of two fish pathogen species of broad-host range, Vibrio harveyi (pVh1) and Photobacterium damselae subsp. damselae (pPHDD1). These data suggest that Vep20 belongs to a new family of plasmid-encoded fish-specific transferrin receptors, and the acquisition of these plasmids through horizontal gene transfer is likely positively selected in the fish-farming environment. Moreover, we propose Ftbp (fish transferrin binding proteins) as a formal name for this family of proteins.
创伤弧菌是一种与人类和鱼类（主要是养殖鳗鱼）疾病相关的海洋细菌，在全球范围内被称为弧菌病。该细菌能够感染和克服鳗鱼先天免疫的能力依赖于一种特定于生物型 2（Bt2）菌株的毒力质粒（pVvbt2）。在本研究中，我们证明了 pVvbt2 编码了一种宿主特异性的铁获取系统，该系统依赖于一种称为 Vep20 的鳗鱼转铁蛋白的外膜受体。vep20 的失活既不影响细菌在人血浆中的生长，也不影响其对小鼠的毒力，而细菌在鳗鱼血液/血浆中的生长被消除，对鳗鱼的毒力显著受损。此外，vep20 是一种铁调节基因，在体外和体内人工诱导的弧菌病期间在鳗鱼血液中过度表达。有趣的是，在两种广泛宿主范围的鱼类病原体物种的可转移质粒中，发现了与 vep20 同源的基因，即哈维氏弧菌（pVh1）和美人鱼发光杆菌亚种美人鱼（pPHDD1）。这些数据表明，Vep20 属于一种新的质粒编码的鱼类特异性转铁蛋白受体家族，并且这些质粒通过水平基因转移的获得在鱼类养殖环境中可能是正选择的。此外，我们提出 Ftbp（鱼类转铁蛋白结合蛋白）作为该蛋白家族的正式名称。
