The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Nankai University, Tianjin 300457, China.
Tianjin Key Laboratory of Microbial Functional Genomics, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin 300457, China.
Int J Mol Sci. 2022 May 16;23(10):5543. doi: 10.3390/ijms23105543.
K1 is the most popular neonatal meningitis-causing Gram-negative bacterium. As a key virulence determinant, the K1 capsule enhances the survival of K1 in human brain microvascular endothelial cells (HBMECs) upon crossing the blood-brain barrier; however, the regulatory mechanisms of capsule synthesis during K1 invasion of HBMECs remain unclear. Here, we identified YbdO as a transcriptional regulator that promotes K1 invasion of HBMECs by directly activating K1 capsule gene expression to increase K1 capsule synthesis. We found that deletion significantly reduced HBMEC invasion by K1 and meningitis occurrence in mice. Additionally, electrophoretic mobility shift assay and chromatin immunoprecipitation-quantitative polymerase chain reaction analysis indicated that YbdO directly activates and expression, which encode products involved in K1 capsule transport and synthesis by directly binding to the promoter. Furthermore, transcription was directly repressed by histone-like nucleoid structuring protein (H-NS), and we observed that acidic pH similar to that of early and late endosomes relieves this transcriptional repression. These findings demonstrated the regulatory mechanism of YbdO on K1 capsule synthesis, providing further insights into the evolution of K1 pathogenesis and host-pathogen interaction.
K1 是最常见的引起新生儿脑膜炎的革兰氏阴性菌。荚膜作为一种关键的毒力决定因素，可增强 K1 通过血脑屏障后在人脑血管内皮细胞（HBMEC）中的存活；然而，荚膜合成的调控机制在 K1 入侵 HBMEC 过程中仍不清楚。本研究鉴定出 YbdO 是一种转录调节因子，可通过直接激活 K1 荚膜基因表达来增加 K1 荚膜合成，从而促进 K1 入侵 HBMEC。研究发现，缺失可显著降低 K1 对 HBMEC 的侵袭和小鼠脑膜炎的发生。此外，凝胶电泳迁移率变动分析和染色质免疫沉淀-定量聚合酶链反应分析表明，YbdO 通过直接结合 启动子，直接激活 和 表达，这两个基因编码与 K1 荚膜转运和合成相关的产物。此外，转录被组蛋白样核小体结构蛋白（H-NS）直接抑制，我们观察到类似于早期和晚期内涵体的酸性 pH 可解除这种转录抑制。这些发现表明了 YbdO 对 K1 荚膜合成的调控机制，为进一步了解 K1 发病机制和宿主-病原体相互作用的进化提供了依据。
