Roles of the regulatory proteins FlhF and FlhG in the Vibrio cholerae flagellar transcription hierarchy
Roles of the regulatory proteins FlhF and FlhG in the Vibrio cholerae flagellar transcription hierarchy
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DOI：
10.1128/jb.187.18.6324-6332.2005
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发表时间：
2005-09-01
影响因子：
3.2
通讯作者：
Klose, KE
中科院分区：
文献类型：
--
作者：
Correa, NE;Peng, F;Klose, KE
霍乱弧菌是人类肠道疾病霍乱的病原体，是一种具有单极鞭毛的运动细菌，运动性被认为是毒力的一个重要方面。1：胆甾鞭毛的层次结构被组织成四类基因。鞭毛层次中每类基因的表达在其他细菌中通常受到正调控元件和负调控元件的严格调控。为了进一步阐明霍乱弧菌鞭毛生物发生的特点，我们的三个假定的调控基因，flhF，flhG和VC 2061的作用。霍乱弧菌flhF和flhG突变体在软琼脂测定中显示不运动。电子显微镜显示flhF突变体缺乏极鞭毛，而有趣的是，flhG突变体每个细胞具有多个（8至10个）极鞭毛。III类和IV类基因启动子的转录活性在flhF突变体中降低，表明FlhF作为III类基因转录的正调控因子。在flhG突变体中所有四类鞭毛启动子的转录增加;表明FlhG充当I类基因转录的负调节剂。此外，对于flhG突变体，定殖幼小鼠肠的能力降低（类似于10倍），表明I类鞭毛基因的负调控增强了毒力。第一：霍乱弧菌VC 2061突变体具有运动性，产生的极鞭毛与野生型无明显区别，四类鞭毛启动子的转录活性与野生型相似。我们的研究结果表明，FlhG和FlhF调节I类和III类鞭毛转录，分别，而VC 2061在I：胆甾鞭毛生物合成中没有检测到的作用。
Vibrio cholerae, the causative agent of the human diarrheal disease cholera, is a motile bacterium with a single polar flagellum, and motility has been inferred to be an important aspect of virulence. The 1: cholerae flagellar hierarchy is organized into four classes of genes. The expression of each class of genes within a flagellar hierarchy is generally tightly regulated in other bacteria by both positive and negative regulatory elements. To further elucidate flagellar biogenesis in V. cholerae, we characterized the roles of the three putative regulatory genes, flhF, flhG and VC2061. V. cholerae flhF and flhG mutants appeared nonmotile in a soft agar assay. Electron microscopy revealed that the flhF mutant lacked a polar flagellum, while interestingly, the flhG mutant possessed multiple (8 to 10) polar flagella per cell. The transcriptional activity of class III and class IV gene promoters in the flhF mutant was decreased, suggesting that FlhF acts as a positive regulator of class III gene transcription. The transcription of all four classes of flagellar promoters was increased in the flhG mutant; suggesting that FlhG acts as a negative regulator of class I gene transcription. Additionally, the ability to colonize the infant mouse intestine was reduced for the flhG mutant (similar to 10-fold), indicating that the negative regulation of class I flagellar genes enhances virulence. The 1: cholerae VC2061 mutant was motile and produced a polar flagellum indistinguishable from that of the wild type, and the transcriptional activities of the four classes of flagellar promoters were similar to that of the wild type. Our results indicate that FlhG and FlhF regulate class I and class III flagellar transcription, respectively, while VC2061 plays no detectable role in I: cholerae flagellar biogenesis.