Andersson Magnus, Uhlin Bernt Eric, Fällman Erik
Department of Physics, Umeå University, Umeå, Sweden.
Biophys J. 2007 Nov 1;93(9):3008-14. doi: 10.1529/biophysj.107.110643. Epub 2007 Aug 3.
Uropathogenic Escherichia coli express pili that mediate binding to host tissue cells. We demonstrate with in situ force measuring optical tweezers that the ability of P and type 1 pili to elongate by unfolding under exposure to stress is a shared property with some differences. The unfolding force of the quaternary structures under equilibrium conditions is similar, 28 +/- 2 and 30 +/- 2 pN for P pili and type 1 pili, respectively. However, type 1 pili are found to be more rigid than P pili through their stronger layer-to-layer bonds. It was found that type 1 pili enter a dynamic regime at elongation speeds of 6 nm/s, compared to 400 nm/s for P pili; i.e., it responds faster to an external force. This possibly helps type 1 to withstand the irregular urine flow in the urethra as compared to the more constant urine flow in the upper urinary tract. Also, it was found that type 1 pili refold during retraction at two different levels that possibly could be related to several possible configurations. Our findings highlight functions that are believed to be of importance for the bacterial ability to sustain a basic antimicrobial mechanism of the host and for bacterial colonization.
尿路致病性大肠杆菌表达菌毛，介导与宿主组织细胞的结合。我们使用原位力测量光镊证明，P菌毛和1型菌毛在应激暴露下通过展开而伸长的能力是一种有差异的共同特性。在平衡条件下，四级结构的展开力相似，P菌毛和1型菌毛分别为28±2和30±2皮牛。然而，通过更强的层间键，发现1型菌毛比P菌毛更坚硬。发现1型菌毛在伸长速度为6纳米/秒时进入动态状态，而P菌毛为400纳米/秒；也就是说，它对外力的反应更快。与上尿路中更稳定的尿流相比，这可能有助于1型菌毛抵御尿道中不规则的尿流。此外，还发现1型菌毛在回缩过程中在两个不同水平上重新折叠，这可能与几种可能的构型有关。我们的发现突出了一些功能，这些功能被认为对于细菌维持宿主基本抗菌机制的能力以及细菌定植很重要。
