Faculty of Materials Science and Engineering , South China University of Technology , Guangzhou 510640 , P. R. China.
Langmuir. 2019 Sep 17;35(37):12257-12263. doi: 10.1021/acs.langmuir.9b02103. Epub 2019 Aug 29.
Surface stiffness plays a critical role in bacterial adhesion, but the mechanism is unclear since the bacterial motion before adhesion is overlooked. Herein, the three-dimensional (3D) motions of and sp. nov 776 onto poly(dimethylsiloxane) (PDMS) surfaces with varying stiffness before adhering were monitored by digital holographic microscopy (DHM). As Young's modulus () of the PDMS surface decreases from 278.1 to 3.4 MPa, the adhered and sp. decrease in number by 40.4 and 34.9%, respectively. Atomic force microscopy (AFM) measurements show that the adhesion force of bacteria to the surface declines with the decreased surface stiffness. In contrast, a nontumbling mutant of adhered (HCB1414 with the adaptive function being partially deficient) decreases much less (by 18.4%). On the other hand, the tumble frequency () of HCB1 and flick frequency () of sp. increase as the surface stiffness decreases, and the motion bias () of sp. also increases. These facts clearly indicate that the bacteria have adapted responses to the surface stiffness. RNA sequencing (RNA-seq) reveals that the downregulated Cph2 and CsrA as well as the upregulated GcvA of swimming HCB1 in bulk near the softer surface promote the bacterial motility.
表面硬度在细菌黏附中起着关键作用，但由于忽视了黏附前细菌的运动，其机制尚不清楚。本文通过数字全息显微镜（DHM）监测了 和 sp. nov 776 在黏附前三维（3D）运动到具有不同硬度的聚二甲基硅氧烷（PDMS）表面上的情况。当 PDMS 表面的杨氏模量（E）从 278.1 MPa 降低到 3.4 MPa 时，黏附的 和 分别减少了 40.4%和 34.9%。原子力显微镜（AFM）测量表明，细菌与表面的黏附力随表面硬度的降低而降低。相比之下，黏附的非翻滚突变体（具有部分适应性功能缺陷的 HCB1414）减少的幅度要小得多（减少 18.4%）。另一方面，滚动频率（HCB1 的 ）和 sp. 的快速游动频率（）随着表面硬度的降低而增加， sp. 的运动偏向性（）也增加。这些事实清楚地表明，细菌对表面硬度有适应性反应。RNA 测序（RNA-seq）表明，在较软表面附近的大量游动 HCB1 中，下调的 Cph2 和 CsrA 以及上调的 GcvA 促进了细菌的运动性。
