直接观察粘附金黄色葡萄球菌27217的细胞壁重塑：一项由SEM和TEM支持的AFM研究
Direct observation of the cell-wall remodeling in adhering Staphylococcus aureus 27217: an AFM study supported by SEM and TEM
摘要：
我们利用原子力显微镜（AFM）的力谱模式来描述的时间演变超过24小时的表面纳米形貌和机械性能的菌株金黄色葡萄球菌27217从细菌粘附到生物膜发生的第一阶段。此外，透射电子显微镜（TEM）和扫描电子显微镜（SEM）实验允许识别两种类型的自粘附亚群（所谓的“秃”和“毛”细胞），并揭示了其相对种群的变化与细菌培养年龄和协议的准备。我们确实观察到了一个戏剧性的消失的“毛茸茸的”亚群的样品进行离心和再悬浮过程。当通过AFM检查时，“毛状”细胞表面类似于人字形结构，其特征在于上部结构单元具有约70 nm的横向尺寸和高杨氏模量值（约2.3 MPa），它们之间的槽的平均深度为约15 nm，并且所得粗糙度为约5 nm。相比之下，“秃”细胞看起来更柔软（~ 0.35 MPa），粗糙度低一个数量级。我们还观察到人字形图案从16小时培养物收获的细胞的“毛状”细菌包膜上逐渐分离，并且它们以球状星团的形式在细菌之间进行性积累。软胞外聚合物物质的分泌也被确定，除了球状星团，可能有助于生物膜空间组织的启动。
英文摘要：
We took benefit from Atomic Force Microscopy (AFM) in the force spectroscopy mode to describe the time evolution-over 24h-of the surface nanotopography and mechanical properties of the strain Staphylococcus aureus 27217 from bacterial adhesion to the first stage of biofilm genesis. In addition, Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) experiments allowed identifying two types of self-adhering subpopulations (the so-called 'bald' and 'hairy' cells) and revealed changes in their relative populations with the bacterial culture age and the protocol of preparation. We indeed observed a dramatic evanescing of the 'hairy' subpopulation for samples that underwent centrifugation and resuspension processes. When examined by AFM, the 'hairy' cell surface resembled to a herringbone structure characterized by upper structural units with lateral dimensions of ~70 nm and a high Young's modulus value (~ 2.3 MPa), a mean depth of the trough between them of ~15nm and a resulting roughness of ~5nm. By contrast, the 'bald' cells appeared much softer (~ 0.35 MPa) with a roughness one order of magnitude lower. We observed too the gradual detachment of the herringbone patterns from the 'hairy' bacterial envelope of cell harvested from a 16h old culture and their progressive accumulation between the bacteria in the form of globular clusters. The secretion of a soft extracellular polymeric substance was also identified that, in addition to the globular clusters, may contribute to the initiation of the biofilm spatial organization.
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