Radhakrishnan Prathima, Theriot Julie A
Department of Biology and Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195-1800.
bioRxiv. 2025 Feb 1:2025.01.31.635960. doi: 10.1101/2025.01.31.635960.
is an intracellular bacterial pathogen that obtains nutrients from the mammalian host cell to fuel its replication in cytosol. Sparse infection of epithelial monolayers by results in the formation of distinct infectious foci, where each focus originates from the initial infection of a single host cell followed by multiple rounds of active bacterial cell-to-cell spread into neighboring host cells in the monolayer. We used time-lapse microscopy to measure changes in bacterial growth rate in individual foci over time and found that intracellular bacteria initially replicate exponentially, but then bacterial growth rate slows later in infection, particularly in the center of the infectious focus. We found that the intracellular replication rate of is measurably decreased by limiting host cell glucose availability, by decreasing the rate of intracellular bacterial oligopeptide import, and, most interestingly, by alterations in host cell junctional proteins that limit bacterial spread into neighboring cells without directly affecting bacterial growth or metabolism. By measuring the carrying capacity of individual host cells, we found that the nutritional density of cytoplasm is comparable to rich medium. Taken together, our results indicate that the rate of intracellular replication is governed by a balance of the rate of nutrient depletion by the bacteria, the rate of nutrient replenishment by the metabolically active host cells, and the rate of bacterial cell-to-cell spread which enables the bacteria to seek out "greener pastures" before nutrient availability in a single host cell becomes limiting.
是一种细胞内细菌病原体，它从哺乳动物宿主细胞获取营养以促进其在细胞质中的复制。上皮单层细胞被稀疏感染会导致形成明显的感染灶，每个感染灶都起源于单个宿主细胞的初始感染，随后细菌会进行多轮活跃的细胞间传播，扩散到单层中的相邻宿主细胞。我们使用延时显微镜来测量单个感染灶中细菌生长速率随时间的变化，发现细胞内细菌最初呈指数级复制，但在感染后期细菌生长速率会减慢，尤其是在感染灶的中心。我们发现，通过限制宿主细胞葡萄糖的可利用性、降低细胞内细菌寡肽的导入速率，以及最有趣的是通过改变宿主细胞连接蛋白来限制细菌扩散到相邻细胞，而不直接影响细菌的生长或代谢，可使的细胞内复制速率显著降低。通过测量单个宿主细胞的承载能力，我们发现细胞质的营养密度与丰富培养基相当。综合来看，我们的结果表明，细胞内复制的速率受细菌营养消耗速率、代谢活跃的宿主细胞营养补充速率以及细菌细胞间传播速率之间平衡的控制，细胞间传播使细菌能够在单个宿主细胞中的营养可用性变得有限之前寻找“更肥沃的牧场”。
