Wang Liyun, Wong Yu-Chern, Correira Joshua M, Wancura Megan, Geiger Chris J, Webster Shanice S, Butler Benjamin J, O'Toole George A, Langford Richard M, Brown Katherine A, Dortdivanlioglu Berkin, Webb Lauren, Cosgriff-Hernandez Elizabeth, Gordon Vernita D
Department of Physics, Center for Nonlinear Dynamics, The University of Texas at Austin, Austin, TX 78712, USA.
Present address: Max Planck Institute for Terrestrial Microbiology, Marburg, 35043, Germany.
bioRxiv. 2023 Jan 27:2023.01.26.525810. doi: 10.1101/2023.01.26.525810.
The attachment of bacteria onto a surface, consequent signaling, and the accumulation and growth of the surface-bound bacterial population are key initial steps in the formation of pathogenic biofilms. While recent reports have hinted that the stiffness of a surface may affect the accumulation of bacteria on that surface, the processes that underlie bacterial perception of and response to surface stiffness are unknown. Furthermore, whether, and how, the surface stiffness impacts biofilm development, after initial accumulation, is not known. We use thin and thick hydrogels to create stiff and soft composite materials, respectively, with the same surface chemistry. Using quantitative microscopy, we find that the accumulation, motility, and growth of the opportunistic human pathogen respond to surface stiffness, and that these are linked through cyclic-di-GMP signaling that depends on surface stiffness. The mechanical cue stemming from surface stiffness is elucidated using finite-element modeling combined with experiments - adhesion to stiffer surfaces results in greater changes in mechanical stress and strain in the bacterial envelope than does adhesion to softer surfaces with identical surface chemistry. The cell-surface-exposed protein PilY1 acts as a mechanosensor, that upon surface engagement, results in higher cyclic-di-GMP levels, lower motility, and greater accumulation on stiffer surfaces. PilY1 impacts the biofilm lag phase, which is extended for bacteria attaching to stiffer surfaces. This study shows clear evidence that bacteria actively respond to different stiffness of surfaces where they adhere perceiving varied mechanical stress and strain upon surface engagement.
细菌附着于表面、随之产生的信号传导以及表面结合细菌群体的积累和生长是致病性生物膜形成的关键初始步骤。虽然最近的报告暗示表面硬度可能会影响细菌在该表面上的积累，但细菌感知和响应表面硬度的潜在过程尚不清楚。此外，在初始积累之后，表面硬度是否以及如何影响生物膜的发育也不清楚。我们分别使用薄水凝胶和厚水凝胶来制造具有相同表面化学性质的硬复合材料和软复合材料。通过定量显微镜观察，我们发现机会性人类病原体的积累、运动性和生长对表面硬度有反应，并且这些反应通过依赖于表面硬度的环二鸟苷酸信号传导联系在一起。利用有限元建模结合实验阐明了源于表面硬度的机械信号——与具有相同表面化学性质的较软表面相比，附着在较硬表面上会导致细菌包膜中的机械应力和应变发生更大的变化。细胞表面暴露的蛋白质PilY1作为一种机械传感器，在与表面接触时，会导致更高的环二鸟苷酸水平、更低的运动性以及在较硬表面上的更多积累。PilY1影响生物膜的延迟期，对于附着在较硬表面上的细菌，该延迟期会延长。这项研究清楚地表明，细菌会积极响应它们所附着表面的不同硬度，在与表面接触时感知到不同的机械应力和应变。
