The composition of intrinsic microbial communities determines if invading pathogens will find a suitable niche for colonization and cause infection or be eliminated. Here, we investigate how commensal E. coli mediate colonization resistance (CR) against Salmonella Typhimurium (S. Tm). Using synthetic bacterial communities, we show that the capacity of E. coli Mt1B1 to block S. Tm colonization depends on the microbial context. In an infection-permissive context, E. coli utilized a high diversity of carbon sources and was unable to block S. Tm invasion. In mice that were stably colonized by twelve phylogenetically diverse murine gut bacteria (OMM¹²), establishing a protective context, E. coli depleted galactitol, a substrate otherwise fueling S. Tm colonization. Here, Lachnospiraceae, capable of consuming C5 and C6 sugars, critically contributed to CR. We propose that E. coli provides CR by depleting a limited carbon source when in a microbial community adept at removing simple sugars from the intestine.

内在微生物群落的组成决定了入侵的病原体是否会找到合适的栖息地并引起感染或被消灭。在这里，我们研究了共生大肠杆菌如何介导针对鼠伤寒沙门氏菌 ( S. Tm) 的定植抗性 (CR )。使用合成细菌群落，我们展示了大肠杆菌Mt1B1 阻断S 的能力。Tm 定植取决于微生物环境。在允许感染的情况下，大肠杆菌利用了高度多样化的碳源并且无法阻止S。Tm入侵。在被 12 种系统发育不同的鼠肠道细菌 (OMM) 稳定定殖的小鼠中¹² )，建立保护环境，大肠杆菌耗尽半乳糖醇，否则为S 提供燃料的底物。Tm 定植。在这里，能够消耗 C5 和 C6 糖的毛螺菌科对 CR 做出了重要贡献。我们建议大肠杆菌在微生物群落中擅长从肠道中去除单糖时，通过消耗有限的碳源来提供 CR。