Functional analysis of a Group A streptococcal locus important for fitness in soft tissue

项目摘要 病原体适应不同环境的能力是其生存、感染、 和持久性。化脓性链球菌（Streptococcus pyogenes，A组 链球菌，GAS）每年导致超过500，000人死亡。即使它通常表现为 浅表感染（如链球菌性咽喉炎），GAS也会导致危及生命的疾病（如坏死性 筋膜炎、中毒性休克综合征），当它从感染的初始部位侵入正常无菌的组织时。它 为了更好地了解GAS的病理生理学及其遗传要求， 需要感染不同的宿主环境我们的实验室进行了体内转座子测序（Tn-seq） 在临床相关的M1 T1 5448 GAS菌株中进行筛选，以确定GAS所需的遗传要求 在上皮下组织中，我们发现了一个以前未表征的位点（scfCDE）， 对这种环境至关重要。仅基于同源性，预测scfCDE编码推定的 ABC进口商。由于该位点以前没有经过实验检验，因此本提案将探讨 scfCDE在GAS细胞途径和毒力中的功能作用，假设scfCDE编码 在宿主组织中GAS适应性中发挥不可或缺作用的膜相关蛋白， 对GAS病理生理学很重要的细胞。本研究将检查scfCDE基因座， 表型在养分利用和胁迫诱导的环境，以确定潜在的基板 这些蛋白质可以转运、探索其遗传结构、表达和操纵子的调节， 最后，探索scfCDE是否对人类血液中的定植、生长和先天性 使用建立的体内和离体GAS感染模型进行免疫逃避。由于scfCDE是 保守的气体和其他厚壁菌门，成功完成这一项目将可能有助于 开发针对GAS和其他重要革兰氏阳性病原体的新治疗策略。

PROJECT SUMMARY A pathogen’s ability to adapt to different environments is an important factor in its survival, infection, and persistence within its host. As a strict human pathogen, Streptococcus pyogenes (Group A Streptococcus, GAS) causes over 500,000 deaths annually. Even though it commonly manifests as superficial infections (e.g. strep throat), GAS also causes life-threatening diseases (e.g. necrotizing fasciitis, toxic shock syndrome) when it invades normally sterile tissues from initial sites of infection. It is imperative to gain a better understanding of GAS pathophysiology and the genetic requirements it needs to infect varying host environments. Our lab performed an in vivo transposon sequencing (Tn-seq) screen in a clinically relevant M1T1 5448 GAS strain to define the genetic requirements needed for GAS fitness in the subepithelial tissue, where we found a previously uncharacterized locus (scfCDE) to be essential for this environment. Based on homology alone, scfCDE are predicted to encode for a putative ABC importer. Because the locus has not been experimentally examined before, this proposal will explore the functional roles of scfCDE in GAS cellular pathways and virulence, hypothesizing that scfCDE encode membrane-associated proteins that play integral roles in GAS fitness in host tissue, importing a substrate into the cell important for GAS pathophysiology. This study will examine the scfCDE locus for phenotypes in nutrient utilization and in stress-induced environments to identify potential substrates these proteins may transport, explore its genetic architecture, expression, and regulation of the operon, and lastly, explore whether scfCDE are important for colonization, growth in human blood, and innate immune evasion using established in vivo and ex vivo models of GAS infection. Since scfCDE are conserved in GAS and other Firmicutes, successful completion of this project will potentially contribute to the development of novel therapeutic strategies against GAS and other important Gram+ pathogens.