Department of Microbiology and Molecular Genetics, University of Texas Health Science Center, Houston, TX 77030;
Division of Oral Biology and Medicine, School of Dentistry, University of California, Los Angeles, CA 90024.
Proc Natl Acad Sci U S A. 2021 Jun 8;118(23). doi: 10.1073/pnas.2006482118.
A gram-negative colonizer of the oral cavity, not only interacts with many pathogens in the oral microbiome but also has the ability to spread to extraoral sites including placenta and amniotic fluid, promoting preterm birth. To date, however, the molecular mechanism of interspecies interactions-termed coaggregation-by and how coaggregation affects bacterial virulence remain poorly defined. Here, we employed genome-wide transposon mutagenesis to uncover fusobacterial coaggregation factors, revealing the intertwined function of a two-component signal transduction system (TCS), named CarRS, and a lysine metabolic pathway in regulating the critical coaggregation factor RadD. Transcriptome analysis shows that CarR modulates a large regulon including and lysine metabolic genes, such as and , the expression of which are highly up-regulated in the Δ mutant. Significantly, the native culture medium of Δ or Δ mutants builds up abundant amounts of free lysine, which blocks fusobacterial coaggregation with streptococci. Our demonstration that lysine-conjugated beads trap RadD from the membrane lysates suggests that lysine utilizes RadD as its receptor to act as a metabolic inhibitor of coaggregation. Lastly, using a mouse model of preterm birth, we show that fusobacterial virulence is significantly attenuated with the Δ and Δ mutants, in contrast to the enhanced virulence phenotype observed upon diminishing RadD (Δ or Δ mutant). Evidently, employs the TCS CarRS and environmental lysine to modulate RadD-mediated interspecies interaction, virulence, and nutrient acquisition to thrive in the adverse environment of oral biofilms and extraoral sites.
一种口腔革兰氏阴性定植菌，不仅与口腔微生物组中的许多病原体相互作用，而且还有能力传播到口腔外部位，包括胎盘和羊水，从而促进早产。然而，迄今为止，种间相互作用（称为共聚）的分子机制以及共聚如何影响细菌毒力仍未得到很好的定义。在这里，我们利用全基因组转座子诱变来揭示梭杆菌的共聚因子，揭示了双组分信号转导系统（TCS）CarRS 和赖氨酸代谢途径在调节关键共聚因子 RadD 中的交织功能。转录组分析表明，CarR 调节一个包括 和赖氨酸代谢基因的大调控子，例如 和 ，其在 Δ 突变体中的表达高度上调。重要的是，Δ 或 Δ 突变体的天然培养基中会积累大量游离赖氨酸，从而阻止了梭杆菌与链球菌的共聚。我们的研究表明，赖氨酸结合珠可从膜提取物中捕获 RadD，这表明赖氨酸利用 RadD 作为其受体，作为共聚的代谢抑制剂。最后，我们使用早产小鼠模型表明，与 Δ 或 Δ 突变体相比，梭杆菌的毒力显著减弱，而降低 RadD（Δ 或 Δ 突变体）则表现出增强的毒力表型。显然， 通过 TCS CarRS 和环境赖氨酸来调节 RadD 介导的种间相互作用、毒力和营养物质获取，以在口腔生物膜和口腔外部位的不利环境中茁壮成长。
