CDI System-mediated Intra- and Inter-species Interactions in Burkholderia

描述（由申请人提供）：革兰氏阴性细菌假马尔杆菌是一种土壤腐殖质和新兴的传染病病原体。它是类鼻疽病的病原体，可导致急性肺部疾病、败血症，如果不及时治疗，可能是致命的。虽然天然存在于东南亚和北澳大利亚，但由于其被武器化的潜力，它引起了全球的关注。细菌通常生活在多微生物群落中，因此进化出了与邻居交流、合作和竞争的机制。其中一种机制是接触依赖性生长抑制（CDI）系统。该系统由双伴侣分泌蛋白组成，并被细菌用来杀死邻近细胞并潜在地控制周围的群体。该系统的主要成分是一个大的表面外蛋白BcpA，它含有一个有毒的c端（CT）。除非目标细胞含有阻断毒性活性的免疫蛋白，否则将CT传递到目标细菌细胞以诱导死亡。CDI系统的一个显著特征是

DESCRIPTION (provided by applicant): The Gram-negative bacterium Burkholderia pseudomallei is a soil saprotroph and an emerging infectious disease agent. It is the causative agent of melioidosis, which can result in acute pulmonary disease, septicemia, and can be fatal if left untreated. Although naturally found in Southeast Asia and Northern Australia, it is of globl concern because of its potential to be weaponized. Bacteria typically live in polymicrobial communities and hence have evolved mechanisms to communicate, cooperate and compete with their neighbors. One such mechanism is the contact-dependent growth inhibition (CDI) system. This system is composed of two-partner secretion proteins, and is utilized by the bacterium to kill neighboring cells and potentially control the surrounding population. The main component of this system is a large surface exoprotein, BcpA, which contains a toxic C-terminus (CT). The CT is delivered to a target bacterial cell to induce death, unless the target cell contains an immunity protein to block the toxic activity. A hallmark feature of CDI systems is polymorphism among CTs and their cognate immunity proteins that protect in an allele specific manner. Studies in our laboratory have shown that the CDI system produced by the non-pathogen B. thailandensis is used for interbacterial competition and biofilm formation. In this proposal we will address several questions regarding Burkholderia-type CDI systems. First we will assess the ability of B. pseudomallei to utilize its CDI systems for interbacterial killing. W will then establish a role for CDI systems in interspecies killing when the bacterium comes into contact with closely related organisms. To achieve this we will evaluate interspecies competition between B. pseudomallei and B. thailandensis. Additionally, through studies using BcpA chimeric proteins, we will analyze regions of BcpA that potentially play a role in activity and specificity of the system. Lastly, we will perform screening analyses to identify the proteins on the target cell that are recognized by the toxin. This step is essential to promote cell-to-cell contact and it defines the specificity of the system. The different aspects that we will investigat in this study will contribute to the understanding of the role of CDI systems within a microbial community. This knowledge can be applied towards biofilm communities that are present in the soil, which is the source of transmission of B. pseudomallei to humans.