Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, 53706 Madison, WI, USA.
Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, 53706 Madison, WI, USA.
Biochim Biophys Acta Biomembr. 2019 Oct 1;1861(10):182990. doi: 10.1016/j.bbamem.2019.05.012. Epub 2019 May 23.
Antimicrobial peptides (AMPs) cause bacterial membrane permeabilization and ultimately cell death at low μM concentrations. The membrane permeabilization action of a moth derived AMP Cecropin A on E. coli cells in exponential growth (mid-log phase) is well studied. At 1× MIC concentration, Cecropin A penetrates the lipopolysaccharide (LPS) barrier and causes outer membrane (OM) and cytoplasmic membrane (CM) permeabilization. For non-septating cells, permeabilization of both membranes begins at one pole. For septating cells, OM permeabilization begins at the septal region and CM permeabilization begins at one pole. However, in nature bacteria are frequently found in nutrient-starved conditions. Here we extend our single-cell microscopy assays to the attack of Cecropin A on E. coli cells in early stationary phase. Stationary phase E. coli is much more resistant to membrane permeabilization by Cecropin A than mid-log phase E. coli. A tenfold higher concentration of Cecropin A is required to observe CM permeabilization in the majority of stationary phase cells, and even then permeabilization proceeds more slowly. In addition, the spatial pattern of initial CM permeabilization changes from localized at one pole to global. Studies of lipid mutant strains suggest that a sufficient localized concentration of the anionic phospholipid phosphatidylglycerol (PG) guides the position of initial attack of the cationic AMP Cecropin A on the CM.
抗菌肽（AMPs）在低 μM 浓度下即可导致细菌膜通透性增加，并最终导致细胞死亡。蛾源性抗菌肽 Cecropin A 对指数生长期（对数中期）大肠杆菌细胞的膜通透性作用已有深入研究。在 1×MIC 浓度下，Cecropin A 穿透脂多糖（LPS）屏障，导致外膜（OM）和细胞质膜（CM）通透性增加。对于非分隔细胞，两膜的通透性均从一个极开始。对于分隔细胞，OM 的通透性从隔膜区域开始，CM 的通透性从一个极开始。然而，在自然界中，细菌经常处于营养饥饿状态。在这里，我们将单细胞显微镜检测方法扩展到 Cecropin A 对早期静止期大肠杆菌细胞的攻击。与对数中期的大肠杆菌相比，静止期的大肠杆菌对 Cecropin A 引起的膜通透性增加的抵抗力要强得多。需要十倍高浓度的 Cecropin A 才能观察到大多数静止期细胞的 CM 通透性增加，即使如此，通透性增加的速度也较慢。此外，初始 CM 通透性增加的空间模式从局部一个极转变为全局。脂质突变株的研究表明，足够局部浓度的阴离子磷脂磷脂酰甘油（PG）指导阳离子抗菌肽 Cecropin A 对 CM 的初始攻击位置。
