Bibek G C, Wu Chenggang
bioRxiv. 2024 Dec 14:2024.12.13.628403. doi: 10.1101/2024.12.13.628403.
Two-component systems (TCS) enable bacteria to sense and respond to environmental signals, facilitating rapid adaptation. , a key oral pathobiont, employs the CarSR TCS to modulate coaggregation with various Gram-positive partners by regulating the expression of , encoding a surface adhesion protein, as revealed by RNA-Seq analysis. However, the direct regulation of the -containing operon ( ) by the response regulator CarR, the broader CarR regulon, and the signals sensed by this system remain unclear. In this study, chromatin immunoprecipitation followed by high-throughput DNA sequencing (ChIP-seq) identified approximately 161 CarR-enriched loci across the genome and a 17-bp consensus motif that likely serves as the CarR binding site. Notably, one such binding motif was found in the promoter region of the operon. The interaction of CarR with this binding motif was further validated using electrophoretic mobility shift assays (EMSA), mutagenesis, and DNase I footprinting analyses. Beyond regulating , CarR directly controls genes involved in fructose and amino acid (cysteine, glutamate, lysine) utilization, underscoring its role as a global regulator in . Lastly, we discovered that RadD-mediated coaggregation enhances expression, and deletion of abolished this enhancement, suggesting that coaggregation itself serves as a signal sensed by this TCS. These findings provide new insights into the CarR regulon and the regulation of RadD, elucidating the ecological and pathogenic roles of in dental plaque formation and disease processes.
is an essential member of oral biofilms, acting as a bridging organism that connects early and late colonizers, thus driving dental plaque formation. Its remarkable ability to aggregate with diverse bacterial partners is central to its ecological success, yet the mechanisms it senses and responds to these interactions remain poorly understood. This study identifies the CarSR two-component system as a direct regulator of RadD, the primary adhesin mediating coaggregation, and reveals its role in sensing coaggregation as a signal. These findings uncover a novel mechanism by which dynamically adapts to polymicrobial environments, offering new perspectives on biofilm formation and bacterial communication in complex oral microbial ecosystems.
双组分系统（TCS）使细菌能够感知并响应环境信号，促进快速适应。如RNA测序分析所示，作为一种关键的口腔致病共生菌，利用CarSR双组分系统通过调节编码表面粘附蛋白的基因的表达，来调节与各种革兰氏阳性菌伙伴的共聚作用。然而，响应调节因子CarR对含基因的操纵子（）的直接调控、更广泛的CarR调控子以及该系统感知的信号仍不清楚。在本研究中，染色质免疫沉淀结合高通量DNA测序（ChIP-seq）在全基因组中鉴定出约161个富含CarR的位点以及一个可能作为CarR结合位点的17bp共有基序。值得注意的是，在操纵子的启动子区域发现了一个这样的结合基序。使用电泳迁移率变动分析（EMSA）、诱变和DNase I足迹分析进一步验证了CarR与该结合基序的相互作用。除了调节基因外，CarR还直接控制参与果糖和氨基酸（半胱氨酸、谷氨酸、赖氨酸）利用的基因，强调了其在中的全局调节作用。最后，我们发现RadD介导的共聚作用增强了基因的表达，而基因的缺失消除了这种增强作用，表明共聚作用本身作为该双组分系统感知的信号。这些发现为CarR调控子和RadD的调节提供了新的见解，阐明了在牙菌斑形成和疾病过程中的生态和致病作用。
是口腔生物膜的重要成员，作为连接早期和晚期定殖菌的桥梁生物，从而推动牙菌斑形成。其与多种细菌伙伴聚集的显著能力是其生态成功的核心，但它感知和响应这些相互作用的机制仍知之甚少。本研究确定CarSR双组分系统是介导共聚作用的主要粘附素RadD的直接调节因子，并揭示了其在将共聚作用感知为信号方面所起的作用。这些发现揭示了一种动态适应多微生物环境的新机制，为复杂口腔微生物生态系统中的生物膜形成和细菌通讯提供了新的视角。
