Institute for Environmental Sciences, University of Kaiserslautern-Landau (RPTU), Landau, Germany.
Institute of Soil Science, Leibniz Universität Hannover, Hannover, Germany.
Sci Rep. 2023 Oct 10;13(1):17146. doi: 10.1038/s41598-023-44256-7.
Studying bacterial adhesion to mineral surfaces is crucial for understanding soil properties. Recent research suggests that minimal coverage of sand particles with cell fragments significantly reduces soil wettability. Using atomic force microscopy (AFM), we investigated the influence of hypertonic stress on Pseudomonas fluorescens adhesion to four different minerals in water. These findings were compared with theoretical XDLVO predictions. To make adhesion force measurements comparable for irregularly shaped particles, we normalized adhesion forces by the respective cell-mineral contact area. Our study revealed an inverse relationship between wettability and the surface-organic carbon content of the minerals. This relationship was evident in the increased adhesion of cells to minerals with decreasing wettability. This phenomenon was attributed to hydrophobic interactions, which appeared to be predominant in all cell-mineral interaction scenarios alongside with hydrogen bonding. Moreover, while montmorillonite and goethite exhibited stronger adhesion to stressed cells, presumably due to enhanced hydrophobic interactions, kaolinite showed an unexpected trend of weaker adhesion to stressed cells. Surprisingly, the adhesion of quartz remained independent of cell stress level. Discrepancies between measured cell-mineral interactions and those calculated by XDLVO, assuming an idealized sphere-plane geometry, helped us interpret the chemical heterogeneity arising from differently exposed edges and planes of minerals. Our results suggest that bacteria may have a significant impact on soil wettability under changing moisture condition.
研究细菌对矿物表面的附着对于理解土壤性质至关重要。最近的研究表明，沙粒表面仅被细胞碎片最小程度覆盖就能显著降低土壤的润湿性。本研究使用原子力显微镜（AFM）研究了高渗应激对荧光假单胞菌在水中附着于四种不同矿物的影响，并与理论 XDLVO 预测进行了比较。为了使不规则形状颗粒的粘附力测量具有可比性，我们通过各自的细胞-矿物接触面积对粘附力进行了归一化。我们的研究表明，润湿性与矿物表面有机碳含量呈反比关系。在润湿性降低的情况下，细胞对矿物的粘附增加，这一关系显而易见。这种现象归因于疏水力，其似乎在所有细胞-矿物相互作用情况下都占主导地位，同时还存在氢键。此外，蒙脱土和针铁矿对受应力细胞的粘附更强，可能是由于增强的疏水力所致，而高岭土对受应力细胞的粘附却出人意料地较弱。令人惊讶的是，石英的粘附力与细胞的应力水平无关。测量的细胞-矿物相互作用与 XDLVO 计算之间的差异，假设理想的球体-平面几何形状，有助于我们解释矿物不同暴露边缘和平面引起的化学异质性。我们的结果表明，细菌在水分变化条件下可能对土壤润湿性有重大影响。
