Characterizing the function and regulation of a conserved virulence-associated genetic pathway of pathogenic Alphaproteobacteria

项目总结 致病细菌使用无数的过程来引起人类疾病，这些过程包括 生物膜的形成、趋化性和运动性，以及分泌系统的实施，所有这些最终都是 帮助在细菌和宿主之间建立密切的联系。几个医学上重要的 细菌，包括一些人类致病的甲型蛋白细菌，极难培养、处理和/或 操纵，因此，与上述过程相关的许多基本毒力机制是 在这些有机体中定义不明确。因此，有许多好处，包括新的治疗方法和疫苗 可以从定义广泛保守的细菌毒力机制中收集到的发展。 考虑到α蛋白细菌的成员，植物病原菌根癌农杆菌 作为研究基本毒力机制的示范模型，这些毒力机制在 甲型变形菌，包括那些引起人类疾病的细菌。根癌农杆菌是一种自由生活的土壤细菌 感知并对受伤植物释放的信号做出反应，导致细菌对 受伤的植物。随后，根癌农杆菌利用IV型分泌系统转移T-DNA复合体 进入植物的细胞中。这种结合事件导致冠胆肿瘤的形成，这是 对植物有严重危害。 初步结果表明，一种LysR型转录调控因子VtlR(用于毒力相关 转录LysR家族调节因子)是根癌农杆菌介导的有效肿瘤形成所必需的。 初步数据表明，根癌农杆菌vtlR缺失菌株产生的数量更少，健壮性更差。 与亲本菌株进行比较，而且vtlR缺失菌株表现出显著的 生物膜形成缺陷。转录分析表明，VtlR控制着一个小分子的表达 称为AbcR1的调控RNA(SRNA)，以及许多其他与接合系统相关的基因， 营养摄取和毒力。与布鲁氏菌密切相关的甲蛋白细菌中的VtlR同源基因 在感染的动物模型中，流产是毒力所必需的，因此，VtlR家族的调节因子高度 在甲型变态杆菌中保守，似乎是宿主-细菌相互作用所必需的。因此， 根癌农杆菌VtlR的系统特征将显著阐明这一机制 转录调节因子与甲型变形菌的毒力有关。

PROJECT SUMMARY Pathogenic bacteria employ myriad processes to cause human disease, and these processes include biofilm formation, chemotaxis and motility, and the implementation of secretion systems, all of which ultimately aid in establishing intimate associations between the bacterium and the host. Several medically important bacteria, including some human pathogenic Alphaproteobateria, are extremely difficult to grow, handle, and/or manipulate, and thus, many of the basic virulence mechanisms related to the processes mentioned above are poorly defined in these organisms. Therefore, there are many benefits, including novel therapeutic and vaccine development that may be gleaned from defining broadly conserved bacterial virulence mechanisms. Considering members of the Alphaproteobacteria, the plant pathogen Agrobacterium tumefaciens serves as an exemplary model for studying basic virulence mechanisms that are highly conserved among the Alphaproteobacteria, including those causing human disease. A. tumefaciens is a free-living soil bacterium that senses and responds to signals released from wounded plants, resulting in bacterial chemotaxis toward the wounded plant. A. tumefaciens subsequently employs a type IV secretion system to transfer a T-DNA complex into the cells of the plant. This conjugation event leads to the formation of crown gall tumors, which are severely detrimental to the plant. Preliminary results indicate a LysR-type transcriptional regulator, VtlR (for virulence-associated transcriptional LysR-family regulator) is required for efficient A. tumefaciens-mediated tumor formation. Preliminary data demonstrate that an A. tumefaciens vtlR deletion strain produces fewer and less robust tumors in potatoes compared to the parental strain, and moreover, the vtlR deletion strain exhibits significant defects in biofilm formation. Transcriptomic analyses revealed that VtlR controls the expression of a small regulatory RNA (sRNA) called AbcR1, as well as a multitude of other genes related to conjugation systems, nutrient uptake, and virulence. The VtlR orthologue in the closely related alphaproteobacterium Brucella abortus is required for virulence in an animal model of infection, and thus, VtlR-family regulators are highly conserved and appear to be required for host-bacteria interactions in the Alphaproteobacteria. Therefore, the systematic characterization of VtlR in A. tumefaciens will significantly illuminate the mechanism by which this transcriptional regulator is linked to virulence in Alphaproteobacteria.