Bacteria from the Turicibacter genus are prominent members of the mammalian gut microbiota and correlate with alterations in dietary fat and body weight, but the specific connections between these symbionts and host physiology are poorly understood. To address this knowledge gap, we characterize a diverse set of mouse- and human-derived Turicibacter isolates, and find they group into clades that differ in their transformations of specific bile acids. We identify Turicibacter bile salt hydrolases that confer strain-specific differences in bile deconjugation. Using male and female gnotobiotic mice, we find colonization with individual Turicibacter strains leads to changes in host bile acid profiles, generally aligning with those produced in vitro. Further, colonizing mice with another bacterium exogenously expressing bile-modifying genes from Turicibacter strains decreases serum cholesterol, triglycerides, and adipose tissue mass. This identifies genes that enable Turicibacter strains to modify host bile acids and lipid metabolism, and positions Turicibacter bacteria as modulators of host fat biology.

Turicibacter属的细菌是哺乳动物肠道微生物群的重要成员，与饮食脂肪和体重的变化相关，但这些共生体与宿主生理学之间的具体联系却知之甚少。为了解决这一知识差距，我们对小鼠和人类来源的Turicibacter分离株进行了表征，发现它们分为在特定胆汁酸转化方面不同的进化枝。我们鉴定了Turicibacter胆汁盐水解酶，其在胆汁解离方面赋予菌株特异性差异。使用雄性和雌性限生小鼠，我们发现单个Turicibacter 的定植菌株会导致宿主胆汁酸谱的变化，通常与体外产生的一致。此外，用另一种外源表达来自Turicibacter菌株的胆汁修饰基因的细菌定植小鼠，可以降低血清胆固醇、甘油三酯和脂肪组织质量。这鉴定了使Turicibacter菌株能够改变宿主胆汁酸和脂质代谢的基因，并将Turicibacter细菌定位为宿主脂肪生物学的调节剂。