Centre for Inflammation and Tissue Repair, Department of Medicine, Royal Free and University College Medical School , Rayne Institute , London WC1E 6JF , United Kingdom.
School of Biological Sciences , Queen's University Belfast , Belfast BT7 1NN , United Kingdom.
ACS Nano. 2020 Jan 28;14(1):1070-1083. doi: 10.1021/acsnano.9b08631. Epub 2020 Jan 8.
In common with many bacterial pathogens, has a polysaccharide capsule which facilitates immune evasion and determines virulence. Recent data have shown that the closely related also expresses polysaccharide capsules including those with an identical chemical structure to capsular serotypes. We utilized atomic force microscopy (AFM) techniques to investigate the biophysical properties of and strains expressing the same capsular serotypes that might relate to differences in virulence potential. When comparing and strains with identical capsule serotypes, strains were susceptible to neutrophil killing, and electron microscopy and AFM demonstrated significant morphological differences. Force-volume mapping using AFM showed distinct force-curve profiles for the center and edge areas of encapsulated streptococcal strains. This "edge effect" was not observed in unencapsulated bacteria and therefore was a direct representation of the mechanical properties of the bacterial capsule. When two strains of and expressed an identical capsular serotype, they presented similar biomechanical characteristics. This infers a potential relationship between capsule biochemistry and nanomechanics, independent of bacterial strain. Overall, this study demonstrates that it is possible to investigate reproducibly the mechanistic, structural, and mechanical properties of both the capsule and the body of individual living bacterial cells and relate the data to virulence phenotypes. We have demonstrated that using nanomechanics to investigate individual bacterial cells we can now begin to identify the surface properties bacterial pathogens require to avoid host-mediated immunity.
与许多细菌病原体一样， 具有多糖荚膜，有助于免疫逃避并决定其毒力。最近的数据表明，密切相关的 也表达多糖荚膜，包括与 荚膜血清型具有相同化学结构的荚膜。我们利用原子力显微镜（AFM）技术研究了表达相同荚膜血清型的 株和 株的生物物理特性，这些特性可能与毒力潜力的差异有关。在比较具有相同荚膜血清型的 株和 株时， 株易被中性粒细胞杀伤，电子显微镜和 AFM 显示出明显的形态差异。使用 AFM 的力-体积映射显示出包裹链球菌菌株中心和边缘区域的明显力曲线特征。这种“边缘效应”在未包裹的细菌中观察不到，因此直接代表了细菌荚膜的机械特性。当 株和 株表达相同的荚膜血清型时，它们表现出相似的生物力学特征。这推断出荚膜生物化学和纳米力学之间存在潜在的关系，与细菌株无关。总的来说，这项研究表明，有可能系统地研究单个活细菌细胞的荚膜和主体的机械、结构和机械特性，并将数据与毒力表型联系起来。我们已经证明，使用纳米力学研究单个细菌细胞，我们现在可以开始确定细菌病原体逃避宿主介导的免疫所需的表面特性。
