Contact-Dependent Interbacterial Signaling in Burkholderia

 描述(申请人提供)：非致病性和致病性伯克霍尔德氏菌，包括引起机会感染的洋葱伯克霍尔德氏菌复合体的成员，编码基因以产生接触依赖性生长抑制(CDI)系统蛋白。CDI是一种广泛存在的现象，在这种现象中，革兰氏阴性细菌利用表面暴露的多态外源蛋白的有毒C末端，在细胞与细胞接触时抑制敏感细菌的生长。外源蛋白毒素被传递到靶细胞的细胞质中，并自我抑制 是通过产生一种小免疫蛋白来预防的。我们先前证明，除了在细菌间竞争中的作用外，由bcpAIOB编码的泰兰伯克霍尔德氏菌的CDI系统蛋白还介导生物膜的形成。这需要BCPA有毒外蛋白的核酸酶活性，但与细菌间的杀伤无关，这表明泰兰杆菌生物膜的形成涉及BCPA的一种未知功能。初步数据表明，bcpAIOB介导了泰兰巴氏杆菌的细菌间信号转导，导致了免疫靶标细菌基因表达的变化。鉴于这些数据和CDI系统的保守性，似乎其他伯克霍尔德氏菌中的CDI系统也在细菌间信号转导中发挥作用，并可能在感染过程中发挥作用。为了理解CDI系统介导的信号转导的作用，这一提议将检验这样的假设，即BCPA毒素传递到免疫靶细胞与特定的周质和细胞质因子相互作用，导致全球基因表达变化，并代表了致病性伯克霍尔德氏菌的有用治疗靶点。目标1中提出的实验将继续研究bcpAIOB介导的细菌间信号转导机制，定义受影响的基因调控途径，确定BCPA所需的区域，以及信号转导所需的其他因素。目标2的研究将探索CDI系统的作用及其作为洋葱伯克霍尔德氏菌复合菌株的治疗方法的潜力。这些研究代表了对可能在革兰氏阴性细菌中广泛存在的现象的首次调查，并将致力于解决对新的药物靶标和抗菌剂的基本需求。

 DESCRIPTION (provided by applicant): Both non-pathogenic and pathogenic Burkholderia, including members of the opportunistic infection-causing Burkholderia cepacia complex, encode genes to produce contact-dependent growth inhibition (CDI) system proteins. CDI is a widespread phenomenon in which Gram-negative bacteria use the toxic C-terminus of a polymorphic surface-exposed exoprotein to inhibit the growth of susceptible bacteria upon cell-cell contact. The exoprotein toxin is delivered to the cytoplasm of target cells and autoinhibition is prevented by production of a small immunity protein. We previously demonstrated that, in addition to their role in interbacterial competition, the CDI system proteins in Burkholderia thailandensis, encoded by bcpAIOB, mediate biofilm formation. This requires the putative nuclease activity of the BcpA toxic exoprotein, but is independent of interbacterial killing, suggesting that biofilm formation in B. thailandensis involves an uncharacterized function of BcpA. Preliminary data suggest that bcpAIOB mediate interbacterial signaling in B. thailandensis, leading to a change in gene expression in immune target bacteria. Given these data and the conservation of CDI systems, it seems likely that CDI systems in other Burkholderia also function in interbacterial signaling and could play a role during infection. Toward understanding the role of CDI system-mediated signaling, this proposal will test the hypothesis that BcpA toxin delivered to an immune target cell interacts with specific periplasmic and cytoplasmic factors, leading to global gene expression changes, and represents a useful therapeutic target in pathogenic Burkholderia. Experiments proposed in Aim 1 will continue to investigate the mechanism of bcpAIOB-mediated interbacterial signaling in B. thailandensis, defining the affected gene regulation pathways and identifying required regions of BcpA, as well as other factors necessary for signaling. Studies in Aim 2 will explore the role of CDI systems and their potential for exploitation as therapies in pathogenic Burkholderia cepacia complex strains. These studies represent the first investigation of what may be a widespread phenomenon in Gram-negative bacteria and will work toward addressing an essential need for new drug targets and antimicrobials.