Department of Chemistry, University of California , Berkeley, California 94720, United States.
Department of Chemistry, Stanford University , Stanford, California 94305, United States.
J Am Chem Soc. 2017 Mar 8;139(9):3488-3495. doi: 10.1021/jacs.6b12541. Epub 2017 Feb 23.
Mycobacteria are endowed with a highly impermeable mycomembrane that confers intrinsic resistance to many antibiotics. Several unique mycomembrane glycolipids have been isolated and structurally characterized, but the underlying organization and dynamics of glycolipids within the cell envelope remain poorly understood. We report here a study of mycomembrane dynamics that was enabled by trehalose-fluorophore conjugates capable of labeling trehalose glycolipids in live actinomycetes. We identified fluorescein-trehalose analogues that are metabolically incorporated into the trehalose mycolates of representative Mycobacterium, Corynebacterium, Nocardia, and Rhodococcus species. Using these probes, we studied the mobilities of labeled glycolipids by time-lapse microscopy and fluorescence recovery after photobleaching experiments and found that mycomembrane fluidity varies widely across species and correlates with mycolic acid structure. Finally, we discovered that treatment of mycobacteria with ethambutol, a front-line tuberculosis (TB) drug, significantly increases mycomembrane fluidity. These findings enhance our understanding of mycobacterial cell envelope structure and dynamics and have implications for development of TB drug cocktails.
分枝杆菌具有高度不透性的菌膜，使其对许多抗生素具有固有抗性。已经分离并结构表征了几种独特的菌膜糖脂，但细胞包膜中糖脂的基本组织和动态仍知之甚少。我们在此报告了一项通过能够标记活放线菌中海藻糖糖脂的海藻糖荧光染料缀合物进行菌膜动力学研究的研究。我们鉴定了荧光素-海藻糖类似物，它们可代谢掺入代表性分枝杆菌、棒状杆菌、诺卡氏菌和红球菌属的海藻糖类脂中。使用这些探针，我们通过延时显微镜和荧光漂白后恢复实验研究了标记糖脂的流动性，发现菌膜流动性在不同物种之间差异很大，并且与类脂酸结构相关。最后，我们发现用一线抗结核（TB）药物乙胺丁醇处理分枝杆菌会显著增加菌膜流动性。这些发现增强了我们对分枝杆菌细胞包膜结构和动力学的理解，并对开发结核病药物鸡尾酒具有重要意义。
