Bile salts, including sodium deoxycholate (DOC), are secreted into the intestine to aid fat digestion and contribute to antimicrobial protection. Gram-negative pathogens such as Escherichia coli, however, are highly resistant to DOC, using multiple mechanisms of which the multidrug efflux pump AcrAB-TolC is the dominant one. Given that TolC-mediated efflux masks the interaction of DOC with potential targets, we sought to identify those targets by identifying genes whose mutations cause an increase in the MIC to DOC relative to the ∆tolC parental strain, that lacks TolC-associated functional efflux pumps. Using a mutant screen, we isolated twenty independent spontaneous mutants that had a higher MICDOC than the E. coli parental ∆tolC strain. Whole genome sequencing of these mutants mapped most mutations to the ptsI or cyaA gene. Analysis of knock-out mutants and complementation showed that elimination of PtsI, a component of the carbohydrate phosphotransferase system, or one of the two key proteins involved in cAMP synthesis and signaling, adenylate cyclase (CyaA) or cAMP receptor protein (Crp) causes low-level increased resistance of a ∆tolC E. coli strain to DOC.

中文翻译：

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不依赖TolC的新机制降低了大肠杆菌中的胆盐敏感性。

胆汁盐，包括脱氧胆酸钠（DOC），被分泌到肠道中以帮助脂肪消化并有助于抗菌保护。但是，革兰氏阴性病原体（例如大肠杆菌）对DOC具有高度抵抗力，其中使用多种机制，其中多药外排泵AcrAB-TolC是主要机制。鉴于TolC介导的外排掩盖了DOC与潜在靶标的相互作用，我们试图通过鉴定突变导致相对于ΔtolC亲本菌株而言MIC到DOC的MIC增加的基因来鉴定那些靶标，而该菌株缺乏与TolC相关的功能外排泵。使用突变体筛选，我们分离了20个独立的自发突变体，它们的MICDOC比大肠杆菌亲本ΔtolC菌株高。这些突变体的全基因组测序将大多数突变定位于ptsI或cyaA基因。