PDF(Pubmed)
Abstract：
Polycationic polymers are widely studied antiseptics, and their efficacy is usually quantified by the solution concentration required to kill a fraction of a population of cells (e.g., by Minimum Bactericidal Concentration (MBC)). Here we describe how the response to a polycationic antimicrobial varies greatly among members of even a monoclonal population of bacteria bathed in a single common antimicrobial concentration. We use fluorescence microscopy to measure the adsorption of a labeled cationic polymer, polydiallyldimethylammmonium chloride (PDADMAC, Mw ≈ 4 × 105 g mol-1) and the time course of cell response via a cell permeability indicator for each member of an ensemble of either Escherichia coli, Staphylococcus aureus, or Pseudomonas aeruginosa cells. This is a departure from traditional methods of evaluating synthetic antimicrobials, which typically measure the overall response of a collection of cells at a particular time and therefore do not assess the diversity within a population. Cells typically die after they reach a threshold adsorption of PDADMAC, but not always. There is a substantial time lag of about 5-10 min between adsorption and death, and the time to die of an individual cell is well correlated with the rate of adsorption. The amount adsorbed and the time-to-die differ among species but follow a trend of more adsorption on more negatively charged species, as expected for a cationic polymer. The study of individual cells via time-lapse microscopy reveals additional details that are lost when measuring ensemble properties at a particular time.
摘要：
聚阳离子聚合物是广泛研究的防腐剂，并且它们的功效通常通过杀死一部分细胞群体所需的溶液浓度来量化（例如，通过最小杀菌浓度(MBC))。在这里，我们描述了对聚阳离子抗微生物剂的反应如何在沐浴在单一常见抗微生物剂浓度中的单克隆细菌群体中的成员之间变化很大。我们使用荧光显微镜来测量标记的阳离子聚合物的吸附，聚二烯丙基二甲基氯化铵(PDADMAC，Mw≈4×105gmol-1）和通过细胞通透性指标对任一大肠杆菌的每个成员的细胞反应的时间过程，金黄色葡萄球菌,或者铜绿假单胞菌细胞.这与传统的评估合成抗菌剂的方法不同，它通常测量细胞集合在特定时间的总体反应，因此不评估群体内的多样性。细胞通常在达到PDADMAC的阈值吸附后死亡，但并非总是如此。在吸附和死亡之间存在约5-10分钟的大量时滞，单个细胞的死亡时间与吸附速率密切相关。物种之间的吸附量和死亡时间不同，但在带负电荷的物种上吸附更多的趋势。正如预期的阳离子聚合物。通过延时显微镜对单个细胞的研究揭示了在特定时间测量整体特性时丢失的其他细节。
