Dorobantu Loredana S, Bhattacharjee Subir, Foght Julia M, Gray Murray R
Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4, Canada.
Langmuir. 2009 Jun 16;25(12):6968-76. doi: 10.1021/la9001237.
Microbial adhesion to surfaces and interfaces is strongly influenced by their structure and physicochemical properties. We used atomic force microscopy (AFM) to measure the forces between chemically functionalized AFM tips and two bacterial species exhibiting different cell surface hydrophobicities, measured as the oil/water contact angle (theta): Acinetobacter venetianus RAG-1 (theta = 56.4 degrees ) and Rhodococcus erythropolis 20S-E1-c (theta = 152.9 degrees ). The forces were measured as the AFM tips, coated with either hydrophobic (octadecane) or hydrophilic (undecanol) groups, approached the bacterial cells in aqueous buffer. The experimental force curves between the two microbial cells and functionalized AFM probes were not successfully described by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory of colloid stability. To reconcile the discrepancy between theory and experiments, two types of extended DLVO models were proposed. The first modification considers an additional acid-base component that accounts for attractive hydrophobic interactions and repulsive hydration effects. The second model considers an additional exponentially decaying steric interaction between polymeric brushes in addition to the acid-base interactions. These extended DLVO predictions agreed well with AFM experimental data for both A. venetianus RAG-1, whose surface consists of an exopolymeric capsule and pili, and R. erythropolis 20S-E1-c, whose surface is covered by an exopolymeric capsule. The extended models for the bacteria-AFM tip force-distance curves were consistent with the effects of steric interactions.
微生物对表面和界面的粘附力受到其结构和物理化学性质的强烈影响。我们使用原子力显微镜（AFM）来测量化学功能化的AFM探针尖端与两种表现出不同细胞表面疏水性的细菌之间的力，疏水性通过油/水接触角（θ）来衡量：鲍曼不动杆菌RAG-1（θ = 56.4度）和红平红球菌20S-E1-c（θ = 152.9度）。在水性缓冲液中，当涂有疏水性（十八烷）或亲水性（十一醇）基团的AFM探针尖端接近细菌细胞时，测量这些力。经典的胶体稳定性德亚金-朗道-韦弗-奥弗贝克（DLVO）理论未能成功描述这两种微生物细胞与功能化AFM探针之间的实验力曲线。为了调和理论与实验之间的差异，提出了两种扩展的DLVO模型。第一种修正考虑了一个额外的酸碱成分，该成分解释了有吸引力的疏水相互作用和排斥性的水合作用。第二种模型除了酸碱相互作用外，还考虑了聚合物刷之间额外的指数衰减空间相互作用。这些扩展的DLVO预测与AFM实验数据非常吻合，无论是表面由胞外聚合物胶囊和菌毛组成的鲍曼不动杆菌RAG-1，还是表面被胞外聚合物胶囊覆盖的红平红球菌20S-E1-c。细菌-AFM探针尖端力-距离曲线的扩展模型与空间相互作用的影响一致。
