Mechanism of Flavobacterium johnsoniae Gliding Motility

滑动运动（细胞在没有鞭毛帮助的情况下在表面上的主动运动）是多种细菌共有的特征。滑行运动在近200年前首次被观察到，但细胞运动的机制仍然是未知的。约翰逊黄杆菌是研究细菌滑动运动的一种方便的模式生物。基因操作技术F。Johnsoniae最近被开发并用于表征滑行所需的许多基因（GLD基因）。由这些基因编码的蛋白质似乎定位于细胞包膜，运动装置预计将驻留在那里。GldA、GldF和GldG被认为相互作用形成ATP结合盒（ABC）转运蛋白。大多数其他Gld蛋白与已知功能的蛋白没有显著的相似性。Gld ABC转运蛋白在滑翔中的作用尚不清楚，将进行研究。野生型和突变型细胞正在进行生物化学表征，以鉴定转运蛋白的货物并确定转运蛋白在滑行中的作用。滑行所需的其他基因也将通过粘粒互补和转座子诱变来鉴定。这些基因将被克隆、测序和分析，以确定滑行机制中各个组成部分的可能功能，在单个gld基因中产生突变，并评估其对细胞运动性的影响。这些基因也将被克隆到表达载体中，以允许Gld蛋白的过量生产。这些蛋白质将被用于产生抗体，这将允许通过细胞分级分离和免疫电子显微镜定位Gld蛋白质。这可能使运动机制首次以高分辨率可视化，并将是确定滑行机制的重要一步。只感染运动细胞的噬菌体也将被用作帮助鉴定运动机制最外层成分的工具。这些研究将有助于更好地了解黄杆菌的滑行运动机制。除了扩大我们对这种常见但知之甚少的细菌运动方式的了解外，这些研究可能具有更大的实用价值，因为滑行细菌与F。约翰逊氏菌作为植物、动物和人类的病原体，作为生物降解的媒介，以及作为酶、抗生素和其它次级代谢物的生产者是重要的。

Gliding motility (the active movement of cells over surfaces without the aid offlagella) is a trait shared by diverse bacteria. Gliding motility was first observed nearly200 years ago, yet the mechanisms responsible for cell movement are still largelyunknown. Flavobacterium johnsoniae is a convenient model organism for studies ofbacterial gliding motility. Techniques to genetically manipulate F. johnsoniae haverecently been developed and used to characterize a number of genes that are requiredfor gliding (gld genes). The proteins encoded by these genes appear to localize to thecell envelope, where the motility apparatus is expected to reside. GldA, GldF, andGldG are thought to interact to form an ATP-binding cassette (ABC) transporter. Mostof the other Gld proteins do not exhibit significant similarity to proteins of knownfunction. The role of the Gld ABC transporter in gliding is not known and will beinvestigated. Wild-type and mutant cells are being biochemically characterized to identifythe cargo of the transporter and determine the role of the transporter in gliding.Additional genes required for gliding will also be identified by cosmid complementationand transposon mutagenesis. These genes will be cloned, sequenced, and analyzed todetermine possible functions for the individual components of the gliding machinery.Mutations will be created in individual gld genes and the effects on cell motility will beassessed. The genes will also be cloned into expression vectors to allowoverproduction of Gld proteins. These proteins will be used to raise antibodies, whichwill allow localization of the Gld proteins by cell fractionation and by immuno-electronmicroscopy. This may allow visualization of the motility machinery at high resolution forthe first time, and will be an important step toward determining the mechanism ofgliding. Bacteriophages that infect only motile cells will also be used as tools to aid inidentification of the outermost components of the motility machinery. These studieswill lead to a better understanding of the mechanism of Flavobacterium gliding motility. In addition to expanding our knowledge on this common but little understood means of bacterial locomotion, these studies could have more practical value since gliding bacteria related to F. johnsoniae are important as pathogens of plants, animals, and humans, as agents of biodegradation, and as producers of enzymes, antibiotics and other secondary metabolites.