Variations in a master regulator affects Clostridioides difficile physiology and virulence

项目总结 艰难梭状芽胞杆菌是一种重要的医院内致病菌，已被归类为 疾控中心的“紧急威胁”。抗生素使用是致病的主要危险因素。 艰难梭菌相关疾病，因为它扰乱了健康的保护性肠道菌群，并使C. 难以在结肠内定植。艰难梭菌通过分泌毒素和 通过形成孢子来传播。编码基因TcdA和TcdB的毒素是一种 致病基因与tcdR正相关。营养素的有效性和其他 环境因素对艰难梭菌毒素的产生有很大影响。科迪，一种在 许多革兰氏阳性细菌是调节主要代谢的重要因素 响应养分供应的途径和毒力基因表达。在艰难梭菌，科迪 通过与配体、GTP和支链氨基结合来感知细胞的营养状态 酸(异亮氨酸、亮氨酸和Valine-ILV)，这种活性Cody然后抑制毒素基因 与tcdR启动子结合并抑制其转录的转录。我们有 艰难梭菌流行株(R20291)的Cody基因存在点突变 这将其第146位的酪氨酸残基改变为天冬酰胺(代号YY146N)。跟随 这种观察，我们在数据库中的搜索导致我们在170多个基因中找到了codYV58A等位基因 不同来源的艰难梭菌不同菌株。类似于Y146(在二聚体界面)，V58是 (ILV结合域)位于Cody的关键位置，并可影响其活性。 初步数据表明，CodYY146N和CodYV58A与野生型Cody在 功能和活动。主调控器活性的任何变化都可以改变基因 其控制下的监管网络。在这项探索性拨款申请中拟议的研究将 确定艰难梭菌因其产生而重新调整的基因调控网络 CodYV58A或CodYY146N，并将评估它们在艰难梭菌生理和发病机制中的作用。

PROJECT SUMMARY Clostridioides difficile is an important nosocomial pathogen that has been classified as an “urgent threat” by CDC. Antibiotic use is the primary risk factor for the development of C. difficile-associated disease because it disrupts healthy protective gut flora and enables C. difficile to colonize the colon. C. difficile damage host tissue by secreting toxins and disseminates by forming spores. The toxins encoding genes, tcdA, and tcdB are part of a pathogenicity locus and are positively regulated by tcdR. Nutrient availability and other environmental factors greatly influence toxin production in C. difficile. CodY, a protein found in many Gram-positive bacterial pathogens, is an important factor that regulates major metabolic pathways and virulence gene expression in response to nutrient availability. In C. difficile, CodY senses the nutritional status of the cell by binding to ligands, GTP, and branched-chain amino acids (Isoleucine, Leucine, and Valine-ILV), and this active CodY then represses toxin genes transcription by binding to the promoter of tcdR and repressing its transcription. We have identified that the codY gene in an epidemic C. difficile strain (R20291) carries a point mutation that changes its Tyrosine residue at the 146th position to an Asparagine (codYY146N). Following this observation, our search in the database leads us to the codYV58A allele in more than 170 different C. difficile strains of different origins. Similar to Y146 (at the dimer interface), V58 is located (ILV binding domain) at a crucial position in CodY and can influence its activity. Preliminary data indicated that CodYY146N and CodYV58A differ from wild-type CodY in their function and activity. Any change in the activity of a master regulator can alter the gene regulatory networks under its control. Proposed studies in this exploratory grant application will identify the readjusted gene regulatory networks in C. difficile because of the production CodYV58A or CodYY146N and will evaluate their effect in C. difficile physiology and pathogenesis.