Interfaculty Institute for Microbiology and Infection Medicine, Department for Microbial Bioactive Compounds, University of Tuebingen, Auf der Morgenstelle 28, 72076 Tuebingen, Germany.
Interfaculty Institute for Microbiology and Infection Medicine, Department for Microbial Bioactive Compounds, University of Tuebingen, Auf der Morgenstelle 28, 72076 Tuebingen, Germany.
Int J Med Microbiol. 2019 Nov;309(7):151329. doi: 10.1016/j.ijmm.2019.151329. Epub 2019 Jul 14.
Antibiotic acyldepsipeptides (ADEPs) exert potent antibacterial activity in rodent models of bacterial infection and exceptional efficacy against persister cells of methicillin-resistant Staphylococcus aureus (MRSA). The mechanism of ADEP action is unusual in that the antibiotic releases the destructive capacity of over-activated ClpP, the proteolytic core of the bacterial Clp protease. The essential bacterial cell division protein FtsZ had emerged in a previous study as a preferred protein substrate of ADEP-activated ClpP but it is definitely not the only cellular substrate. In the current study, we set out to follow the morphological changes that lead to ADEP-mediated bacterial death in S. aureus and Bacillus subtilis, differentiating between antibacterial effects at low and high ADEP concentrations. Here, fluorescence and time-lapse microscopy data show that cells adopt a characteristic phenotype of cell division inhibition at ADEP levels close to the MIC, but retain the capacity to form viable daughter cells for a substantial period of time when transferred to ADEP-free growth medium. After extended exposure to low ADEP concentrations, nucleoids of B. subtilis started to disorganize and upon compound removal many cells failed to re-organize nucleoids, re-initiate cytokinesis and consequently died. Survival versus cell death of filamentous cells attempting recovery depended on the timing of completion of new septa in relation to the loss of cell envelope integrity. We show that the potential to recover after ADEP removal depends on the antibiotic concentration as well as the treatment duration. When exposed to ADEP at concentrations well above the MIC, biomass production ceased rapidly as did the potential to recover. In time-kill studies both long-time exposure to low ADEP levels as well as short-time exposure to high concentrations proved highly effective, while intermittent concentrations and time frames were not. We here provide new insights into the antimicrobial activity of ADEP antibiotics and the consequences of dosing and timing for bacterial physiology which should be considered in view of a potential therapeutic application of ADEPs.
抗生素酰基二肽（ADEPs）在细菌感染的啮齿动物模型中表现出强大的抗菌活性，对耐甲氧西林金黄色葡萄球菌（MRSA）的持久性细胞具有出色的疗效。ADEP 作用的机制不寻常，因为抗生素释放出过度激活的 ClpP 的破坏能力，ClpP 是细菌 Clp 蛋白酶的核心蛋白酶。在之前的一项研究中，必需的细菌细胞分裂蛋白 FtsZ 作为 ADEP 激活的 ClpP 的首选蛋白底物出现，但它肯定不是唯一的细胞底物。在本研究中，我们着手研究导致金黄色葡萄球菌和枯草芽孢杆菌中 ADEP 介导的细菌死亡的形态变化，区分低浓度和高浓度 ADEP 时的抗菌作用。在这里，荧光和延时显微镜数据显示，当 ADEP 水平接近 MIC 时，细胞会表现出细胞分裂抑制的特征表型，但在转移到不含 ADEP 的生长培养基后，仍有很长一段时间保持形成有活力的子细胞的能力。在长时间暴露于低浓度 ADEP 后，枯草芽孢杆菌的核体开始解体，当去除化合物后，许多细胞无法重新组织核体，重新开始细胞分裂，最终死亡。尝试恢复的丝状细胞的存活与细胞死亡取决于新隔膜完成的时间与细胞包膜完整性丧失的时间之间的关系。我们表明，在去除 ADEP 后恢复的潜力取决于抗生素浓度以及处理持续时间。当暴露于高于 MIC 的 ADEP 浓度时，生物量的产生迅速停止，恢复的潜力也随之停止。在时间杀伤研究中，长时间暴露于低 ADEP 水平和短时间暴露于高浓度都被证明非常有效，而间歇性浓度和时间框架则不然。我们在这里提供了关于 ADEP 抗生素的抗菌活性以及对细菌生理学的剂量和时间的影响的新见解，在考虑 ADEP 的潜在治疗应用时应考虑这些因素。
