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

项目摘要 致病细菌利用无数过程引起人类疾病，这些过程包括 生物膜形成、趋化性和运动性以及分泌系统的实施，所有这些最终 有助于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，包括一些人类致病性α蛋白细菌，极难生长、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 在这些生物体中定义不清。因此，有许多好处，包括新的治疗和疫苗 这可能是从定义广泛保守的细菌毒力机制中收集到的。 考虑到阿尔法变形菌门的成员，植物病原体根癌农杆菌 作为研究基本毒力机制的示范模型，这些机制在细菌中高度保守。 α-变形菌，包括那些引起人类疾病的。A.根瘤菌是一种自由生活的土壤细菌， 感受并响应受伤植物释放的信号，导致细菌对植物的趋化性。 受伤的植物A.根癌农杆菌随后使用IV型分泌系统来转移T-DNA复合物 进入植物的细胞。这种接合事件导致冠瘿瘤的形成， 对植物极为有害。 初步结果表明，LysR型转录调节因子VtlR（用于与细胞毒相关的基因） 转录LysR家族调节子）是高效A. tumefaciens介导的肿瘤形成。 初步数据表明，A.根癌农杆菌vtlR缺失菌株产生较少且较不稳健的 与亲本菌株相比，vtlR缺失菌株在马铃薯中的肿瘤中表现出显著的生长抑制作用，并且此外，vtlR缺失菌株表现出显著的生长抑制作用。 生物膜形成缺陷。转录组学分析显示，VtlR控制一个小的表达。 称为AbcR 1的调节RNA（sRNA），以及与接合系统相关的许多其他基因， 营养吸收和毒性。布鲁氏杆菌中的VtlR同源基因 在感染的动物模型中，牛流产病毒是毒力所需的，因此，VtlR家族调节剂高度依赖于牛流产病毒。 保守的，似乎是所需的宿主-细菌相互作用的α变形菌。因此 对A.根癌农杆菌将显著阐明这一机制， 转录调节因子与α变形菌中的毒力有关。

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.