Unit of Sexually Transmitted Bacterial Pathogens and HIV, Robert Koch Institute, Berlin, Germany.
Unit of Advanced Light and Electron Microscopy, Robert Koch Institute, Berlin, Germany.
mBio. 2024 Aug 14;15(8):e0128824. doi: 10.1128/mbio.01288-24. Epub 2024 Jul 23.
The egress of intracellular bacteria from host cells and cellular tissues is a critical process during the infection cycle. This process is essential for bacteria to spread inside the host and can influence the outcome of an infection. For the obligate intracellular Gram-negative zoonotic bacterium little is known about the mechanisms resulting in bacterial egress from the infected epithelium. Here, we describe and characterize -containing spheres (CCSs), a novel and predominant type of non-lytic egress utilized by spp. CCSs are spherical, low-phase contrast structures surrounded by a phosphatidylserine-exposing membrane with specific barrier functions. They contain infectious progeny and morphologically impaired cellular organelles. CCS formation is a sequential process starting with the proteolytic cleavage of a DEVD tetrapeptide-containing substrate that can be detected inside the chlamydial inclusions, followed by an increase in the intracellular calcium concentration of the infected cell. Subsequently, blebbing of the plasma membrane begins, the inclusion membrane destabilizes, and the proteolytic cleavage of a DEVD-containing substrate increases rapidly within the whole infected cell. Finally, infected, blebbing cells detach and leave the monolayer, thereby forming CCS. This sequence of events is unique for chlamydial CCS formation and fundamentally different from previously described egress pathways. Thus, CCS formation represents a major, previously uncharacterized egress pathway for intracellular pathogens that could be linked to biology in general and might influence the infection outcome .IMPORTANCEHost cell egress is essential for intracellular pathogens to spread within an organism and for host-to-host transmission. Here, we characterize -containing sphere (CCS) formation as a novel and predominant non-lytic egress pathway of the intracellular pathogens and . CCS formation is fundamentally different from extrusion formation, the previously described non-lytic egress pathway of . CCS formation is a unique sequential process, including proteolytic activity, followed by an increase in intracellular calcium concentration, inclusion membrane destabilization, plasma membrane blebbing, and the final detachment of a whole phosphatidylserine-exposing former host cell. Thus, CCS formation represents an important and previously uncharacterized egress pathway for intracellular pathogens that could possibly be linked to biology, including host tropism, protection from host cell defense mechanisms, or bacterial pathogenicity.
细胞内细菌从宿主细胞和组织中逸出是感染周期中的一个关键过程。这个过程对于细菌在宿主内部的传播至关重要，并可能影响感染的结果。对于专性细胞内革兰氏阴性动物病原体 ，我们知之甚少的是导致细菌从受感染的上皮细胞逸出的机制。在这里，我们描述并表征了 - 包含球体（CCSs），这是一种新型且主要的非溶细胞逸出方式，由 种属利用。CCs 是球形的，低相衬度结构，周围环绕着暴露磷脂酰丝氨酸的膜，具有特定的屏障功能。它们包含有感染性的后代和形态受损的细胞细胞器。CCs 的形成是一个连续的过程，从包含 DEVD 四肽的底物的蛋白水解切割开始，该切割可在衣原体包涵体内检测到，随后感染细胞的细胞内钙离子浓度增加。随后，质膜开始起泡，包含体膜不稳定，并且包含 DEVD 底物的蛋白水解切割在整个感染细胞内迅速增加。最后，感染的起泡细胞脱落并离开单层，从而形成 CCS。这种事件序列是衣原体 CCS 形成所特有的，与先前描述的 逸出途径根本不同。因此，CCs 的形成代表了一种主要的、以前未被描述的细胞内病原体逸出途径，可能与一般的 生物学有关，并可能影响感染结果。
重要性宿主细胞逸出对于细胞内病原体在生物体内部传播以及宿主间传播至关重要。在这里，我们将 - 包含球体（CCS）的形成描述为细胞内病原体 和 的一种新型且主要的非溶细胞逸出途径。CCS 的形成与挤出形成根本不同，挤出形成是先前描述的 的非溶细胞逸出途径。CCS 的形成是一个独特的连续过程，包括蛋白水解活性，随后是细胞内钙离子浓度的增加、包含体膜的不稳定、质膜起泡和整个暴露磷脂酰丝氨酸的前宿主细胞的最终脱落。因此，CCS 的形成代表了一种重要的、以前未被描述的细胞内病原体逸出途径，可能与 生物学有关，包括宿主嗜性、逃避宿主细胞防御机制或细菌致病性。
