Mularski Anna, Wilksch Jonathan J, Wang Huabin, Hossain Mohammed Akhter, Wade John D, Separovic Frances, Strugnell Richard A, Gee Michelle L
†School of Chemistry, ‡Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, and §Florey Institute for Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC 3010, Australia.
Langmuir. 2015 Jun 9;31(22):6164-71. doi: 10.1021/acs.langmuir.5b01011. Epub 2015 May 26.
Increasing rates of antimicrobial-resistant medically important bacteria require the development of new, effective therapeutics, of which antimicrobial peptides (AMPs) are among the promising candidates. Many AMPs are membrane-active, but their mode of action in killing bacteria or in inhibiting their growth remains elusive. This study used atomic force microscopy (AFM) to probe the mechanobiology of a model AMP (a derivative of melittin) on living Klebsiella pneumoniae bacterial cells. We performed in situ biophysical measurements to understand how the melittin peptide modulates various biophysical behaviors of individual bacteria, including the turgor pressure, cell wall elasticity, and bacterial capsule thickness and organization. Exposure of K. pneumoniae to the peptide had a significant effect on the turgor pressure and Young's modulus of the cell wall. The turgor pressure increased upon peptide addition followed by a later decrease, suggesting that cell lysis occurred and pressure was lost through destruction of the cell envelope. The Young's modulus also increased, indicating that interaction with the peptide increased the rigidity of the cell wall. The bacterial capsule did not prevent cell lysis by the peptide, and surprisingly, the capsule appeared unaffected by exposure to the peptide, as capsule thickness and inferred organization were within the control limits, determined by mechanical measurements. These data show that AFM measurements may provide valuable insights into the physical events that precede bacterial lysis by AMPs.
具有医学重要性的细菌对抗菌素的耐药率不断上升，这就需要开发新的有效治疗方法，其中抗菌肽（AMPs）是有前景的候选者之一。许多抗菌肽具有膜活性，但其杀死细菌或抑制其生长的作用方式仍不清楚。本研究使用原子力显微镜（AFM）来探究一种模型抗菌肽（蜂毒肽衍生物）对活的肺炎克雷伯菌细胞的力学生物学作用。我们进行了原位生物物理测量，以了解蜂毒肽如何调节单个细菌的各种生物物理行为，包括膨压、细胞壁弹性以及细菌荚膜厚度和组织结构。肺炎克雷伯菌暴露于该肽对细胞壁的膨压和杨氏模量有显著影响。添加肽后膨压先升高，随后降低，这表明细胞发生了裂解，压力通过细胞膜的破坏而丧失。杨氏模量也增加了，表明与该肽的相互作用增加了细胞壁的刚性。细菌荚膜并不能阻止该肽引起的细胞裂解，令人惊讶的是，荚膜似乎未受该肽暴露的影响，因为通过机械测量确定的荚膜厚度和推断的组织结构在对照范围内。这些数据表明，AFM测量可为抗菌肽引起细菌裂解之前的物理事件提供有价值的见解。
