Rashid Maheen, Tachiyama Shoichi, Zhu Shiwei, Zhao Hang, McCaig William D, Sun Jingchuan, Li Huilin, Liu Jun, Thanassi David G
Department of Microbiology and Immunology, Renaissance School of Medicine, Stony Brook University, Stony Brook, New York, USA.
Center for Infectious Diseases, Stony Brook University, Stony Brook, New York, USA.
mBio. 2025 Jun 11;16(6):e0106025. doi: 10.1128/mbio.01060-25. Epub 2025 May 19.
is a gram-negative, intracellular pathogen that causes the zoonotic disease tularemia. Due to its ease of dissemination and high lethality, is classified as a tier 1 select agent with potential for misuse as a bioweapon. The mechanisms by which replicates intracellularly and interacts with the host during infection are not well understood. produces spherical outer membrane vesicles (OMVs) and novel tubular extensions of its cell surface that are also released extracellularly. These OMV and outer membrane tubes (OMTs) contain virulence factors and are produced in response to amino acid starvation and during infection of macrophages. To investigate how the OMTs are formed, we used cryogenic electron tomography to examine the model spp., , during culture and within the macrophage phagosome. OMT formation involved progressive alterations of the bacterial envelope, resulting in extensions of both the inner and outer membranes. A dynamic cytoplasmic structure was present at the base of the OMT that extended into the tubes during elongation, together with cytoplasmic material. OMT produced within the macrophage phagosome was associated with changes to the phagosomal membrane, suggesting a role in phagosomal escape. Consistent with this, using confocal microscopy, we observed co-localization of the type VI secretion system with the OMT, both within bacteria and in released tubular vesicles. These findings reveal the cellular transformations that occur during membrane tubulation by and provide insights into the function of membrane-derived structures during host-pathogen interactions.
is an intracellular bacterial pathogen that causes the zoonotic disease tularemia. Following uptake by host cells, the bacteria rapidly escape the phagosome and replicate intracellularly. In previous studies, we found that produces tubular extensions of its cell surface in response to specific cues and during macrophage infection. In the present study, we used cryogenic electron tomography to examine tube formation by the model sp., . This analysis revealed that tube formation involves extensive bacterial envelope alterations and a dynamic cytoplasmic organelle. Furthermore, tubes produced by bacteria within infected macrophages were associated with the breakdown of the phagosomal membrane. In addition, we found that the type VI secretion system, which is essential for phagosomal escape, co-localized with the bacterial tubes. These findings reveal the cellular transformations that occur during membrane tubulation by and suggest a role for the tubes in phagosomal escape.
是一种革兰氏阴性细胞内病原体，可引起人畜共患疾病兔热病。由于其易于传播且致死率高，被列为一级选择制剂，有被滥用作生物武器的潜在风险。其在细胞内复制以及在感染期间与宿主相互作用的机制尚不清楚。会产生球形外膜囊泡（OMV）及其细胞表面新的管状延伸物，这些也会释放到细胞外。这些OMV和外膜管（OMT）含有毒力因子，是在氨基酸饥饿和巨噬细胞感染期间产生的。为了研究OMT是如何形成的，我们使用低温电子断层扫描来检查模式菌种在培养期间和巨噬细胞吞噬体内的情况。OMT的形成涉及细菌包膜的渐进性改变，导致内膜和外膜都延伸。在OMT的基部存在一个动态的细胞质结构，在延伸过程中会延伸到管内，同时还有细胞质物质。在巨噬细胞吞噬体内产生的OMT与吞噬体膜的变化有关，表明其在吞噬体逃逸中起作用。与此一致，使用共聚焦显微镜，我们观察到VI型分泌系统与OMT在细菌内和释放的管状囊泡中都共定位。这些发现揭示了在形成膜管过程中发生的细胞转变，并为膜衍生结构在宿主 - 病原体相互作用中的功能提供了见解。
是一种细胞内细菌病原体，可引起人畜共患疾病兔热病。被宿主细胞摄取后，细菌迅速逃离吞噬体并在细胞内复制。在先前的研究中，我们发现会根据特定信号并在巨噬细胞感染期间产生其细胞表面的管状延伸物。在本研究中，我们使用低温电子断层扫描来检查模式菌种形成管的情况。该分析表明，管的形成涉及广泛的细菌包膜改变和一个动态的细胞质细胞器。此外，受感染巨噬细胞内的细菌产生的管与吞噬体膜的破裂有关。此外，我们发现对吞噬体逃逸至关重要的VI型分泌系统与细菌管共定位。这些发现揭示了在形成膜管过程中发生的细胞转变，并表明管在吞噬体逃逸中起作用。
