College of Pharmaceutical Sciences, Matsuyama University, 4-2 Bunkyo-cho, Matsuyama, Ehime 790-8578, Japan.
Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan.
Microbiology (Reading). 2012 Aug;158(Pt 8):2039-2049. doi: 10.1099/mic.0.059568-0. Epub 2012 Jun 14.
We determined the ability of Vibrio parahaemolyticus to utilize enterobactin (Ent) as a xenosiderophore. Homology searches of the V. parahaemolyticus genomic sequence revealed the presence of genes that are homologous to the V. cholerae ferric Ent utilization genes, which consist of the iron-repressible outer-membrane protein genes irgA and vctA, and the ATP-binding cassette transport system operon vctPDGC. Moreover, the irgB and vctR genes, which encode transcriptional regulators, were also found immediately upstream of irgA and vctA, respectively. Growth assays of V. parahaemolyticus indicated that both irgA and vctA mutants grew well in the presence of Ent under iron-limiting conditions, whereas both the irgA/vctA double mutant and the vctPDGC mutant barely grew under the same conditions. In addition, growth assays of three isogenic tonB mutants demonstrated that the TonB2 system, and to a lesser extent the TonB1 system, can provide energy for both IrgA and VctA to transport ferric Ent. SDS-PAGE analysis showed that expression of both IrgA and VctA was enhanced by the presence of Ent. Complementation of the irgB and vctR mutants with their respective genes resulted in the increased expression of IrgA and VctA, respectively. Finally, reverse transcriptase-quantitative PCR revealed that transcription of the Ent utilization system genes is iron-regulated, and that transcription of irgA and vctA under iron-limiting conditions is further activated by proteins encoded by irgB and vctR, respectively, together with Ent.
我们确定了副溶血性弧菌利用肠铁载体（Ent）作为外铁载体的能力。副溶血性弧菌基因组序列的同源性搜索显示存在与霍乱弧菌铁 Ent 利用基因同源的基因，这些基因包括铁抑制的外膜蛋白基因 irgA 和 vctA，以及 ATP 结合盒转运系统操纵子 vctPDGC。此外，还发现了编码转录调节剂的 irgB 和 vctR 基因，分别位于 irgA 和 vctA 的上游。副溶血性弧菌的生长实验表明，irgA 和 vctA 突变体在铁限制条件下 Ent 存在时生长良好，而 irgA/vctA 双突变体和 vctPDGC 突变体在相同条件下几乎无法生长。此外，三种同基因 tonB 突变体的生长实验表明，TonB2 系统，在较小程度上 TonB1 系统，可以为 IrgA 和 VctA 转运铁 Ent 提供能量。SDS-PAGE 分析表明，Ent 的存在增强了 IrgA 和 VctA 的表达。irgB 和 vctR 突变体与它们各自的基因互补导致 IrgA 和 VctA 的表达分别增加。最后，逆转录定量 PCR 显示 Ent 利用系统基因的转录受铁调控，并且在铁限制条件下，irgA 和 vctA 的转录分别被 irgB 和 vctR 编码的蛋白进一步激活，同时 Ent 也被激活。
