Laboratory of Molecular Microbiology, Research and Innovation Complex "Nanobiotechnologies", Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russia.
Faculty of Biology, Shenzhen MSU-BIT University, Dayun New Town, Longgang District, Shenzhen, China.
J Virol. 2024 Oct 22;98(10):e0020524. doi: 10.1128/jvi.00205-24. Epub 2024 Sep 11.
During infection, the giant phiKZ phage forms a specialized structure at the center of the host cell called the phage nucleus. This structure is crucial for safeguarding viral DNA against bacterial nucleases and for segregating the transcriptional activities of late genes. Here, we describe a morphological entity, the early phage infection (EPI) vesicle, which appears to be responsible for earlier gene segregation at the beginning of the infection process. Using cryo-electron microscopy, electron tomography (ET), and fluorescence microscopy with membrane-specific dyes, we demonstrated that the EPI vesicle is enclosed in a lipid bilayer originating, apparently, from the inner membrane of the bacterial cell. Our investigations further disclose that the phiKZ EPI vesicle contains both viral DNA and viral RNA polymerase (vRNAP). We have observed that the EPI vesicle migrates from the cell pole to the center of the bacterial cell together with ChmA, the primary protein of the phage nucleus. The phage DNA is transported into the phage nucleus after phage maturation, but the EPI vesicle remains outside. We hypothesized that the EPI vesicle acts as a membrane transport agent, efficiently delivering phage DNA to the phage nucleus while protecting it from the nucleases of the bacterium.
Our study shed light on the processes of phage phiKZ early infection stage, expanding our understanding of possible strategies for the development of phage infection. We show that phiKZ virion content during injection is packed inside special membrane structures called early phage infection (EPI) membrane vesicles originating from the bacterial inner cell membrane. We demonstrated the EPI vesicle fulfilled the role of the safety transport unit for the phage genome to the phage nucleus, where the phage DNA would be replicated and protected from bacterial immune systems.
在感染过程中，巨型 phiKZ 噬菌体在宿主细胞的中心形成一种称为噬菌体核的特殊结构。该结构对于保护病毒 DNA 免受细菌核酸酶的侵害以及分隔晚期基因的转录活性至关重要。在这里，我们描述了一种形态实体，早期噬菌体感染（EPI）囊泡，它似乎负责在感染过程开始时更早地分隔早期基因。使用冷冻电子显微镜、电子断层扫描（ET）和带有膜特异性染料的荧光显微镜，我们证明了 EPI 囊泡被包裹在起源于细菌细胞内膜的脂质双层中。我们的研究进一步揭示了 phiKZ EPI 囊泡包含病毒 DNA 和病毒 RNA 聚合酶（vRNAP）。我们观察到 EPI 囊泡与噬菌体核的主要蛋白 ChmA 一起从细胞极迁移到细菌细胞的中心。噬菌体 DNA 在噬菌体成熟后被运入噬菌体核，但 EPI 囊泡仍留在外面。我们假设 EPI 囊泡充当膜运输剂，在将噬菌体 DNA 有效递送至噬菌体核的同时保护其免受细菌核酸酶的侵害。
我们的研究阐明了噬菌体 phiKZ 早期感染阶段的过程，扩展了我们对噬菌体感染发展的可能策略的理解。我们表明，在注入过程中，phiKZ 病毒粒子的内容物被包装在特殊的膜结构中，称为早期噬菌体感染（EPI）膜囊泡，这些囊泡起源于细菌内膜。我们证明 EPI 囊泡充当了噬菌体基因组到噬菌体核的安全运输单位，噬菌体 DNA 将在那里复制并免受细菌免疫系统的侵害。
