Allen Christopher A, Niesel David W, Torres Alfredo G
Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-1070, USA.
Environ Microbiol. 2008 Jun;10(6):1512-25. doi: 10.1111/j.1462-2920.2008.01567.x. Epub 2008 Feb 26.
The impact of low-shear stress (LSS) was evaluated on an Adherent-invasive Escherichia coli clinical isolate (AIEC strain O83:H1) from a Crohn's disease patient. High-aspect ratio vessels (HARVs) were used to model LSS conditions to characterize changes in environmental stress resistance and adhesion/invasive properties. Low-shear stress-grown cultures exhibited enhanced thermal and oxidative stress resistance as well as increased adherence to Caco-2 cells, but no changes in invasion were observed. An AIEC rpoS mutant was constructed to examine the impact of this global stress regulator. The absence of RpoS under LSS conditions resulted in increased sensitivity to oxidative stress while adherence levels were elevated in comparison with the wild-type strain. TnphoA mutagenesis and rpoS complementation were carried out on the rpoS mutant to identify those factors involved in the LSS-induced adherence phenotype. Mutagenesis results revealed that one insertion disrupted the tnaB gene (encoding tryptophan permease) and the rpoS tnaB double mutant exhibited decreased adherence under LSS. Complementation of the tnaB gene, or medium supplemented with exogenous indole, restored adhesion of the rpoS tnaB mutant under LSS conditions. Overall, our study demonstrated how mechanical stresses such as LSS altered AIEC phenotypic characteristics and identified novel functions for some RpoS-regulated proteins.
对一名克罗恩病患者的粘附侵袭性大肠杆菌临床分离株（AIEC菌株O83:H1）评估了低剪切应力（LSS）的影响。使用高纵横比血管（HARV）模拟LSS条件，以表征环境应激抗性和粘附/侵袭特性的变化。低剪切应力培养的细菌表现出增强的热应激和氧化应激抗性以及对Caco-2细胞粘附增加，但未观察到侵袭的变化。构建了AIEC rpoS突变体以检查这种全局应激调节因子的影响。在LSS条件下RpoS的缺失导致对氧化应激的敏感性增加，而与野生型菌株相比粘附水平升高。对rpoS突变体进行TnphoA诱变和rpoS互补，以鉴定参与LSS诱导的粘附表型的那些因子。诱变结果表明，一个插入破坏了tnaB基因（编码色氨酸通透酶），并且rpoS tnaB双突变体在LSS下表现出降低的粘附。tnaB基因的互补或补充有外源吲哚的培养基恢复了rpoS tnaB突变体在LSS条件下的粘附。总体而言，我们的研究证明了诸如LSS之类的机械应力如何改变AIEC表型特征，并确定了一些RpoS调节蛋白的新功能。
