拟杆菌是人类肠道微生物群的重要成员,有助于营养交换,肠道功能,以及宿主免疫系统的成熟。这种专性的厌氧菌共生体可以采用生物膜的生活方式,最近表明,胆汁的存在促进了B.thetaiotaomicron生物膜的形成。此过程还需要B.thetaiotaomicron胞外DNA酶,这不是,然而,由胆汁调节。这里,我们发现胆汁诱导几种抗性结瘤分裂(RND)外排泵的表达,并且用全球竞争性外排抑制剂抑制其活性会损害胆汁依赖性生物膜的形成。然后我们证明了,在胆汁诱导的RND外排泵中,只有BT3337-BT3338-BT3339三方泵,改名为BipABC[用于胆汁诱导泵A(BT3337),B(BT3338),和C(BT3339)],是生物膜形成所必需的。我们证明了BipABC参与镁向生物膜细胞外基质的外排,这导致细胞外DNA浓度的降低。生物膜基质中镁的释放也会影响生物膜结构,潜在地通过改变矩阵内的静电斥力,减少细菌间距离,让细菌更紧密地相互作用,形成更致密的生物膜。因此,我们的研究,确定了响应胆汁盐的B.thetaiotaomicron生物膜形成的新分子决定因素,并提供了对肠道化学线索如何调节主要肠道共生体中生物膜形成的更好理解。IMPORTANCEBacterioidesthetaiotaomicron是人类肠道微生物群的重要成员,能够降解饮食和宿主多糖,完全有助于营养交换,肠道功能,以及宿主免疫系统的成熟。这种专性的厌氧菌共生体可以采用生物膜社区的生活方式,提供针对环境因素的保护,反过来,保护宿主免受菌群失调和菌群失调相关疾病的侵害。最近表明,B.thetaiotaomicron暴露于肠胆汁促进生物膜形成。这里,我们揭示了一个特定的B.thetaiotaomicron膜外排泵是响应胆汁诱导,导致镁离子的释放,潜在地降低生物膜基质组分之间的静电斥力。这导致细菌间距离的减小并增强生物膜结构。我们的研究,因此,更好地了解胆汁如何促进主要肠道共生体中的生物膜形成,可能促进微生物区对压力和菌群失调事件的恢复力。
Bacteroides thetaiotaomicron is a prominent member of the human gut microbiota contributing to nutrient exchange, gut function, and maturation of the host\'s immune system. This obligate anaerobe symbiont can adopt a biofilm lifestyle, and it was recently shown that B. thetaiotaomicron biofilm formation is promoted by the presence of bile. This process also requires a B. thetaiotaomicron extracellular DNase, which is not, however, regulated by bile. Here, we showed that bile induces the expression of several Resistance-Nodulation-Division (RND) efflux pumps and that inhibiting their activity with a global competitive efflux inhibitor impaired bile-dependent biofilm formation. We then showed that, among the bile-induced RND-efflux pumps, only the tripartite BT3337-BT3338-BT3339 pump, re-named BipABC [for Bile Induced Pump A (BT3337), B (BT3338), and C (BT3339)], is required for biofilm formation. We demonstrated that BipABC is involved in the efflux of magnesium to the biofilm extracellular matrix, which leads to a decrease of extracellular DNA concentration. The release of magnesium in the biofilm matrix also impacts biofilm structure, potentially by modifying the electrostatic repulsion forces within the matrix, reducing interbacterial distance and allowing bacteria to interact more closely and form denser biofilms. Our study therefore, identified a new molecular determinant of B. thetaiotaomicron biofilm formation in response to bile salts and provides a better understanding on how an intestinal chemical cue regulates biofilm formation in a major gut symbiont.IMPORTANCEBacteroides thetaiotaomicron is a prominent member of the human gut microbiota able to degrade dietary and host polysaccharides, altogether contributing to nutrient exchange, gut function, and maturation of the host\'s immune system. This obligate anaerobe symbiont can adopt a biofilm community lifestyle, providing protection against environmental factors that might, in turn, protect the host from dysbiosis and dysbiosis-related diseases. It was recently shown that B. thetaiotaomicron exposure to intestinal bile promotes biofilm formation. Here, we reveal that a specific B. thetaiotaomicron membrane efflux pump is induced in response to bile, leading to the release of magnesium ions, potentially reducing electrostatic repulsion forces between components of the biofilm matrix. This leads to a reduction of interbacterial distance and strengthens the biofilm structure. Our study, therefore, provides a better understanding of how bile promotes biofilm formation in a major gut symbiont, potentially promoting microbiota resilience to stress and dysbiosis events.