1D5_7.fastqDivergent Roles of hcp Genes in Salmonella Typhimurium T6SS Shape Gut Microbiota Dysbiosis during InfectionT6SS

Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) is a facultative intracellular pathogen causing significant gastrointestinal infections in humans and animals. The type VI secretion system (T6SS) plays a crucial role in its virulence, facilitating competition with host gut microbiota and promoting infection. While S. Typhimurium possesses a single T6SS, it encodes three hcp genes, which are crucial for its functionality and may exhibit non-redundant roles. In this study, we used 16S rRNA sequencing to analyze gut microbiota in BALB/c mice after infection with wild-type (WT) S. Typhimurium or mutant strains (Δhcp1, Δhcp2, Δhcp3). Our findings revealed that S. Typhimurium infection induced severe gut dysbiosis especially on the second day post-infection. Specifically, the infection led to a notable increase in Firmicutes and activated the energy pathways that promotes the breakdown of short chain fatty acids. Wild type S. Typhimurium infection caused a sharp increase in Escherichia-Shigella levels, indicating inflammation-related dysbiosis, while the Δhcp1, Δhcp2, and Δhcp3 groups showed milder changes, suggesting less disruption to gut microbiota. Deletion of individual hcp genes led to distinct bacterial taxa changes, underscoring the non-redundant functions of each hcp. Despite having only one T6SS, S. Typhimurium achieves precise modulation of its functions through the divergent roles of its Hcp proteins, enabling efficient colonization and persistence in the host gut.  These findings provide insights into the intricate mechanisms of bacterial adaptation and host-pathogen interactions, offering potential avenues for therapeutic interventions targeting T6SS-mediated dysbiosis.

肠炎沙门氏菌肠炎亚种鼠伤寒血清型（Salmonella enterica subsp. enterica serovar Typhimurium，S. Typhimurium）是一种兼性胞内致病菌，可引发人与动物的严重胃肠道感染。VI型分泌系统（type VI secretion system, T6SS）在其毒力发挥中至关重要，能够介导其与宿主肠道菌群的竞争并促进感染进程。尽管S. Typhimurium仅携带一套T6SS，但其基因组编码3个hcp基因，这些基因对T6SS功能至关重要且可能发挥非冗余的作用。本研究采用16S rRNA测序技术，分析了BALB/c小鼠感染野生型（wild-type, WT）S. Typhimurium或其Δhcp1、Δhcp2、Δhcp3突变菌株后的肠道菌群组成。研究结果显示，S. Typhimurium感染可诱导小鼠出现严重的肠道菌群失调，尤其在感染后第2天最为显著。具体而言，感染可导致厚壁菌门（Firmicutes）丰度显著升高，并激活促进短链脂肪酸（short chain fatty acids）分解的能量代谢通路。野生型S. Typhimurium感染可引发埃希氏菌-志贺氏菌属（Escherichia-Shigella）丰度急剧上升，提示存在炎症相关的菌群失调；而Δhcp1、Δhcp2及Δhcp3突变组的菌群变化则更为温和，表明其对肠道菌群的破坏程度更低。单个hcp基因的缺失会导致独特的细菌类群变化，进一步证实了各Hcp蛋白的非冗余功能。尽管仅拥有一套T6SS，S. Typhimurium通过各Hcp蛋白的差异化功能实现了对其功能的精准调控，从而得以在宿主肠道中高效定植并持续存活。本研究结果为解析细菌适应与宿主-病原体互作的复杂机制提供了新视角，也为靶向T6SS介导的菌群失调的治疗干预策略提供了潜在方向。