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PLoS Biology：细菌“力大无比”zz
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（奈瑟氏球菌落及放射性菌毛的免疫荧光图片 来源：science daily） 亚利桑那大学和哥伦比亚大学的科学家最近研究发现细菌的菌毛“力大无比”，可以移动自身质量十万倍的物体。 研究人员通过对淋病奈瑟氏球菌（生物谷注：Neisseria gonorrhoeae）实验，一束菌毛收缩时的力量可达到单跟菌毛的十多倍。这种驱动收缩的分子马达是已知动力最强的纳米生物马达。通过对菌毛的研究可以帮助解决各种致病菌的治疗难题。这项研究的论文发表在最新一期的《公共图书馆 生物学》上面。（生物谷编译） 生物谷推荐原始出处： doi:10.1371/journal.pbio.0060087 （PLoS Biology ）April 15, 2008 Cooperative Retraction of Bundled Type IV Pili Enables Nanonewton Force Generation Nicolas Biais1, Benoît Ladoux2, Dustin Higashi3, Magdalene So3, Michael Sheetz1* 1 Department of Biological Sciences, Columbia University, New York, New York, United States of America, 2 Matière et Systèmes Complexes, CNRS UMR7057/Université Paris 7, Bâtiment Condorcet, 75205 Paris cedex 13, France, 3 Department of Immunobiology, BIO5 Institute, University of Arizona, Tucson, Arizona, United States of America The causative agent of gonorrhea, Neisseria gonorrhoeae, bears retractable filamentous appendages called type IV pili (Tfp). Tfp are used by many pathogenic and nonpathogenic bacteria to carry out a number of vital functions, including DNA uptake, twitching motility (crawling over surfaces), and attachment to host cells. In N. gonorrhoeae, Tfp binding to epithelial cells and the mechanical forces associated with this binding stimulate signaling cascades and gene expression that enhance infection. Retraction of a single Tfp filament generates forces of 50–100 piconewtons, but nothing is known, thus far, on the retraction force ability of multiple Tfp filaments, even though each bacterium expresses multiple Tfp and multiple bacteria interact during infection. We designed a micropillar assay system to measure Tfp retraction forces. This system consists of an array of force sensors made of elastic pillars that allow quantification of retraction forces from adherent N. gonorrhoeae bacteria. Electron microscopy and fluorescence microscopy were used in combination with this novel assay to assess the structures of Tfp. We show that Tfp can form bundles, which contain up to 8–10 Tfp filaments, that act as coordinated retractable units with forces up to 10 times greater than single filament retraction forces. Furthermore, single filament retraction forces are transient, whereas bundled filaments produce retraction forces that can be sustained. Alterations of noncovalent protein–protein interactions between Tfp can inhibit both bundle formation and high-amplitude retraction forces. Retraction forces build over time through the recruitment and bundling of multiple Tfp that pull cooperatively to generate forces in the nanonewton range. We propose that Tfp retraction can be synchronized through bundling, that Tfp bundle retraction can generate forces in the nanonewton range in vivo, and that such high forces could affect infection. |
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