Surface lipids on pathogenic mycobacteria modulate infection outcomes by regulating host immune responses. Phenolic glycolipid (PGL) is a host-modulating surface lipid that varies among clinical Mycobacterium tuberculosis strains. PGL is also found in Mycobacterium marinum, where it promotes infection of zebrafish through effects on the innate immune system. Given the important role this lipid plays in the host–pathogen relationship, tools for profiling its abundance, spatial distribution, and dynamics are needed. Here, we report a strategy for imaging PGL in live mycobacteria using bioorthogonal metabolic labeling. We functionalized the PGL precursor p-hydroxybenzoic acid (pHB) with an azide group (3-azido pHB). When fed to mycobacteria, 3-azido pHB was incorporated into the cell surface, which could then be visualized via the bioorthogonal conjugation of a fluorescent probe. We confirmed that 3-azido pHB incorporates into PGL using mass spectrometry methods and demonstrated selectivity for PGL-producing M. marinum and M. tuberculosis strains. Finally, we applied this metabolic labeling strategy to study the dynamics of PGL within the mycobacterial membrane. This new tool enables visualization of PGL that may facilitate studies of mycobacterial pathogenesis.

中文翻译：

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分枝杆菌毒力因子酚糖脂的生物正交代谢标记

致病性分枝杆菌的表面脂质通过调节宿主免疫反应来调节感染结果。酚糖脂 (PGL) 是一种宿主调节表面脂质，在临床结核分枝杆菌菌株之间存在差异。PGL 也存在于海分枝杆菌中，它通过影响先天免疫系统促进斑马鱼的感染。鉴于这种脂质在宿主-病原体关系中发挥的重要作用，需要用于分析其丰度、空间分布和动态的工具。在这里，我们报告了一种使用生物正交代谢标记对活分枝杆菌中 PGL 进行成像的策略。我们用叠氮基（3-叠氮基p HB）对PGL 前体对羟基苯甲酸（p HB）进行功能化。当喂食分枝杆菌时，3-叠氮基p HB 被掺入细胞表面，然后可以通过荧光探针的生物正交缀合进行可视化。我们使用质谱方法证实了 3-叠氮基p HB 并入 PGL，并证明了对产生 PGL 的M. marinum和M. tuberculosis菌株的选择性。最后，我们应用这种代谢标记策略来研究分枝杆菌膜内 PGL 的动态。这种新工具可以实现 PGL 的可视化，从而有助于分枝杆菌发病机制的研究。