Cell-cell signaling, gene expression, and horizontal gene transfer in Bacillus

描述（申请人提供）：细胞-细胞信号传导控制着生物世界的许多过程，包括发育、发病、生长、转化和交配。信号传导过程通常由一些细胞产生并被其他细胞感知的扩散因子（如激素、信息素、神经递质）介导。除了可扩散的信号分子外，细胞间通讯的一种最亲密的形式包括偶联和水平基因转移。微生物的交配反应通常是由肽信息素介导的。该项目的长期目标是了解细胞如何调节基因表达和水平基因转移以响应环境条件，重点是细胞-细胞信号传导和控制枯草芽孢杆菌中移动遗传元件的调节机制。可移动遗传元件包括噬菌体、共轭质粒和共轭转座子，也称为整合和共轭元件（ICEs）。移动遗传元件在进化、基因组可塑性、共生、发病机制和抗生素耐药性传播等方面发挥着重要作用。尽管它们很重要，但对革兰氏阳性生物中ICEs的调节机制知之甚少。移动遗传因子ICEBs1是枯草芽孢杆菌的整合偶联基因。它驻留在枯草芽孢杆菌的染色体上，并稳定地与宿主染色体一起繁殖。ICEBs1基因的表达、切除、复制和交配受细胞-细胞信号反应调控，并在DNA损伤时诱导（SOS反应）。该项目将重点研究ICEBs1的调控机制和功能，这些机制似乎是广泛保守的，但在革兰氏阳性中尚未得到很好的理解。该项目包括：阐明保守的抗抑制因子和抑制因子介导的诱导机制及其通过DNA损伤和细胞-细胞信号传导的调节；确定供体细胞切除后ICEBs1的复制机制和功能，以及复制如何促进ICEBs1的水平基因转移和稳定性；确定保守细胞-细胞信号模块在控制其他移动元件水平基因转移中的作用。枯草芽孢杆菌是一种相对简单的、可通过实验获得的微生物，我们对枯草芽孢杆菌中细胞-细胞信号传导、基因表达和水平基因转移的研究，应该为许多生物中使用的一般机制提供见解。公共卫生相关性：微生物中的移动遗传元件和水平基因转移对抗生素耐药性的发病和传播起着重要作用。该项目调查了在许多不同生物体中发现的一种常见类型的可移动遗传元件，特别是革兰氏阳性细菌，如金黄色葡萄球菌、肺炎链球菌、粪肠球菌和炭疽芽孢杆菌，它们会导致严重的人类疾病。

DESCRIPTION (provided by applicant): Cell-cell signaling controls many processes in the biological world, including development, pathogenesis, growth, transformation, and mating. Signaling processes are often mediated by diffusible factors (e.g., hormones, pheromones, neurotransmitters) that are produced by some cells and sensed by others. In addition to diffusible signaling molecules, one of the most intimate forms of cell-cell communication involves conjugation and horizontal gene transfer. Mating responses in microbes are often mediated by peptide pheromones. The long term goal of this project is to understand how cells modulate gene expression and horizontal gene transfer in response to environmental conditions, with emphasis on cell-cell signaling and the regulatory mechanisms controlling a mobile genetic element in the bacterium Bacillus subtilis. Mobile genetic elements include phages, conjugative plasmids, and conjugative transposons, also known as integrative and conjugative elements (ICEs). Mobile genetic elements play significant roles in evolution, genome plasticity, symbiosis, pathogenesis, and the spread of antibiotic resistance. Despite their importance, relatively little is known about the mechanisms regulating ICEs in Gram-positive organisms. The mobile genetic element ICEBs1 is an integrative and conjugative element in Bacillus subtilis. It resides in the B. subtilis chromosome and is stably propagated with the host chromosome. ICEBs1 gene expression, excision, replication, and mating are regulated by a cell-cell signaling response and induced upon DNA damage (the SOS response). This project will focus on mechanisms of ICEBs1 regulation and function that appear to be broadly conserved and that are not well-understood in Gram-positives. The project includes: elucidation of the mechanisms of induction mediated by a conserved anti-repressor and repressor and their regulation by DNA damage and cell-cell signaling; determination of the mechanisms and functions of replication of ICEBs1 in donor cells after excision and how replication contributes to horizontal gene transfer and stability of ICEBs1; determination of roles of conserved cell-cell signaling modules in the control of horizontal gene transfer in other mobile elements. Our studies on cell-cell signaling, gene expression, and horizontal gene transfer in B. subtilis, a relatively simple, experimentally accessible microbe, should provide insights into general mechanisms used in many organisms. PUBLIC HEALTH RELEVANCE: Mobile genetic elements and horizontal gene transfer in microbes contribute significantly to pathogenesis and the spread of antibiotic resistances. This project investigates a common type of mobile genetic element that is found in many different organisms, especially Gram-positive bacteria exemplified by Staphylococcus aureus, Streptococcus pneumoniae, Enterococcus faecalis and Bacillus anthracis, that cause serious human disease.