Schembri M A, Christiansen G, Klemm P
Microbial Adhesion Group, Section of Molecular Microbiology, BioCentrum-DTU, Bldg 301, Technical University of Denmark, DK-2800 Lyngby, Denmark.
Mol Microbiol. 2001 Sep;41(6):1419-30. doi: 10.1046/j.1365-2958.2001.02613.x.
Autoaggregation is a phenomenon thought to contribute to colonization of mammalian hosts by pathogenic bacteria. Type 1 fimbriae are surface organelles of Escherichia coli that mediate d-mannose-sensitive binding to various host surfaces. This binding is conferred by the minor fimbrial component FimH. In this study, we have used random mutagenesis to identify variants of the FimH adhesin that confer the ability of E. coli to autoaggregate and settle from liquid cultures. Three separate autoaggregating clones were identified, all of which contained multiple amino acid changes located within the N-terminal receptor-binding domain of FimH. Autoaggregation could not be inhibited by mannose, but was inhibited by growth at temperatures at or below 30 degrees C. Using green fluorescent protein (GFP) as a reporter, we show that the autoaggregating clones do not mix with wild-type fimbriated cells. Electron microscopy shows that autoaggregating cells produce fimbriae with a twisted and entangled appearance. We present evidence that autoaggregating versions of FimH also occur in nature. Our results stress the highly adaptive nature of the ubiquitous FimH adhesin.
自身聚集是一种被认为有助于病原菌在哺乳动物宿主体内定殖的现象。1型菌毛是大肠杆菌的表面细胞器，介导对多种宿主表面的d-甘露糖敏感结合。这种结合由菌毛次要成分FimH赋予。在本研究中，我们利用随机诱变来鉴定赋予大肠杆菌从液体培养物中自身聚集和沉降能力的FimH黏附素变体。鉴定出三个独立的自身聚集克隆，它们均在FimH的N端受体结合域内含有多个氨基酸变化。自身聚集不能被甘露糖抑制，但在30摄氏度或更低温度下生长会受到抑制。使用绿色荧光蛋白（GFP）作为报告基因，我们表明自身聚集克隆不会与野生型菌毛化细胞混合。电子显微镜显示，自身聚集细胞产生的菌毛呈扭曲和缠结状。我们提供证据表明，FimH的自身聚集变体在自然界中也存在。我们的结果强调了普遍存在的FimH黏附素的高度适应性。
