Khare Somya, Hsin Jen, Sorto Nohemy A, Nepomuceno Gabriella M, Shaw Jared T, Shi Handuo, Huang Kerwyn Casey
Department of Bioengineering, Stanford University, Stanford, CA, 94305, USA.
Department of Chemistry, University of California at Davis, Davis, CA, 95616, USA.
Adv Biosyst. 2019 Nov;3(11):e1900021. doi: 10.1002/adbi.201900021. Epub 2019 Jun 21.
While cell division is a critical process in cellular proliferation, very few antibiotics have been identified that target the bacterial cell-division machinery. Recent studies have shown that the small molecule PC190723 inhibits cell division in several Gram-positive bacteria, with a hypothesized mechanism of action involving direct targeting of the tubulin homolog FtsZ, which is essential for division in virtually all bacterial species. Here, it is shown that PC190723 also inhibits cell division in the Gram-negative bacterium Escherichia coli if the outer membrane permeability barrier is compromised genetically or chemically. The results show that the equivalent FtsZ mutations conferring PC190723 resistance in Staphylococcus aureus do not protect E. coli against PC190723, and that suppressors of PC190723 sensitivity in E. coli, which do not generically decrease outer membrane permeability, do not map to FtsZ or other division proteins. These suppressors display a wide range of morphological and growth phenotypes, and one exhibits a death phenotype in the stationary phase similar to that of a mutant with disrupted lipid homeostasis. Finally, a complementing FtsZ-msfGFP fusion is used to show that PC190723 does not affect the Z-ring structure. Taken together, the findings suggest that PC190723 inhibits growth and division in E. coli without targeting FtsZ. This study highlights the importance of utilizing a combination of genetic, chemical, and single-cell approaches to dissect the mechanisms of action of new antibiotics, which are not necessarily conserved across bacterial species.
虽然细胞分裂是细胞增殖中的一个关键过程，但已鉴定出的靶向细菌细胞分裂机制的抗生素非常少。最近的研究表明，小分子PC190723可抑制几种革兰氏阳性菌的细胞分裂，其推测的作用机制涉及直接靶向微管蛋白同源物FtsZ，而FtsZ实际上对所有细菌物种的分裂都是必不可少的。本文表明，如果外膜通透性屏障在基因上或化学上受到破坏，PC190723也会抑制革兰氏阴性菌大肠杆菌的细胞分裂。结果表明，在金黄色葡萄球菌中赋予PC190723抗性的等效FtsZ突变并不能保护大肠杆菌免受PC190723的影响，而且在大肠杆菌中PC190723敏感性的抑制子（它们一般不会降低外膜通透性）并不定位于FtsZ或其他分裂蛋白。这些抑制子表现出广泛的形态和生长表型，其中一个在稳定期表现出死亡表型，类似于脂质稳态被破坏的突变体。最后，利用互补的FtsZ-msfGFP融合蛋白表明PC190723不影响Z环结构。综上所述，这些发现表明PC190723在不靶向FtsZ的情况下抑制大肠杆菌的生长和分裂。这项研究强调了利用遗传、化学和单细胞方法相结合来剖析新型抗生素作用机制的重要性，这些机制在不同细菌物种中不一定是保守的。
