Klinth Jeanna E, Castelain Mickaël, Uhlin Bernt Eric, Axner Ove
Department of Physics, Umeå University, Umeå, Sweden.
PLoS One. 2012;7(6):e38548. doi: 10.1371/journal.pone.0038548. Epub 2012 Jun 5.
Adhesion to host tissues is an initiating step in a majority of bacterial infections. In the case of Gram-negative bacteria this adhesion is often mediated by a specific interaction between an adhesin, positioned at the distal end of bacterial pili, and its receptor on the surface of the host tissue. Furthermore, the rod of the pilus, and particularly its biomechanical properties, is believed to be crucial for the ability of bacteria to withstand external forces caused by, for example, (in the case of urinary tract infections) urinary rinsing flows by redistributing the force to several pili. In this work, the adhesion properties of P-piliated E. coli and their dependence of pH have been investigated in a broad pH range by both the surface plasmon resonance technique and force measuring optical tweezers. We demonstrate that P piliated bacteria have an adhesion ability throughout the entire physiologically relevant pH range (pH 4.5 - 8). We also show that pH has a higher impact on the binding rate than on the binding stability or the biomechanical properties of pili; the binding rate was found to have a maximum around pH 5 while the binding stability was found to have a broader distribution over pH and be significant over the entire physiologically relevant pH range. Force measurements on a single organelle level show that the biomechanical properties of P pili are not significantly affected by pH.
对宿主组织的黏附是大多数细菌感染的起始步骤。对于革兰氏阴性菌而言，这种黏附通常由位于菌毛远端的黏附素与其在宿主组织表面的受体之间的特异性相互作用介导。此外，菌毛杆，尤其是其生物力学特性，被认为对于细菌通过将力重新分配到几根菌毛来抵抗例如（在尿路感染的情况下）尿液冲洗流动所引起的外力的能力至关重要。在这项工作中，通过表面等离子体共振技术和测力光镊在较宽的pH范围内研究了P菌毛大肠杆菌的黏附特性及其对pH的依赖性。我们证明P菌毛细菌在整个生理相关pH范围（pH 4.5 - 8）内都具有黏附能力。我们还表明，pH对结合速率的影响比对菌毛的结合稳定性或生物力学特性的影响更大；发现结合速率在pH约为5时达到最大值，而结合稳定性在pH范围内分布更广，并且在整个生理相关pH范围内都很显著。在单个细胞器水平上的力测量表明，P菌毛的生物力学特性不受pH的显著影响。
