Mechanisms and regulation of replication, the cell cycle, gene expression, and horizontal gene transfer in prokaryotes, focusing on Bacillus subtilis

我们的长期目标是了解许多基本的分子机制和调控 细菌中的细胞过程。我们对控制DNA复制特别感兴趣，细胞 复制、环境传感和信号转导中对扰动的反应和机制 控制水平基因转移。我们在这些研究中选择的生物体是革兰氏阳性细菌 枯草杆菌。关于枯草杆菌的信息非常丰富。它很容易在基因上种植和操纵 它与几种病原体和环境细菌有关，这些细菌在实验上不太容易处理。 水平基因转移是微生物进化的驱动力。它在很大程度上是通过移动设备进行中介的 遗传元件，包括病毒、接合质粒、整合和接合元件(ICE， 也称为共轭转座子)。共轭元素是众所周知的代理人，有助于 抗生素耐药性、致病机制、共生、新陈代谢等基因的传播。 尽管冰雪的流行和重要性，但我们对它们的理解仍然存在缺陷。 元素，特别是在革兰氏阳性细菌中。我们的工作将集中在枯草杆菌中ICEBs1的生命周期。这个 在实验中在群体中90%的细胞中诱导ICEBs1并实现相对较高的接合的能力 频率将允许我们回答以前对ICE生命周期基本的困难或未研究的问题。 我们还将识别和分析ICE功能所需的宿主基因，并研究ICE和ICE之间的相互作用。 细胞中的其他可移动元素。我们将把我们的分析扩展到Tn916，一种广泛参与传播的ICE 四环素抗药性。我们的发现应该与生长在细菌之间的基因转移有关 许多不同的环境，包括人类微生物群。 我们的工作还将集中在染色体动力学和基因表达的几个方面。细胞有 用于调节复制启动的多种机制。细胞也有调节反应 复制中的扰动，通常被称为检查点，控制基因表达和细胞周期进展。 将基因表达和细胞周期进展与染色体复制和完整性结合起来有助于防止 产生染色体有缺陷的细胞。基因组复制与细胞周期的协调 进展对于细胞分化和防止失控的细胞生长是重要的。微生物 发病机制通常依赖于宿主内正常的细菌复制和生长。 我们将使用体内和体外的各种途径和方法来表征： 复制启动的控制；复制启动子和转录因子DNAA的调节；以及基因 受控制以响应复制过程中的扰动。了解枯草杆菌的这些过程将提供 对各种生物体中类似过程和同源蛋白质的洞察，包括许多 革兰氏阳性病原体。

Our long term goals are to understand many of the molecular mechanisms and regulation underlying basic cellular processes in bacteria. We are particularly interested in the control of DNA replication, cellular responses to perturbations in replication, environmental sensing and signal transduction, and mechanisms controlling horizontal gene transfer. Our organism of choice for these studies is the Gram positive bacterium Bacillus subtilis. There is a wealth of information about B. subtilis. It is easy to grow and manipulate genetically and is related to several pathogens and environmental bacteria that are less tractable experimentally. Horizontal gene transfer (HGT) is the driving force in microbial evolution. It is largely mediated by mobile genetic elements, including viruses, conjugative plasmids, and integrative and conjugative elements (ICEs, also known as conjugative transposons). Conjugative elements are well known agents contributing to the spread of genes for antibiotic resistances, pathogenesis, symbiosis, metabolism, and more. Despite the prevalence and importance of ICEs, there are deficiencies in our understanding of these elements, especially in Gram positive bacteria. Our work will focus on the lifecycle of ICEBs1 in B. subtilis. The ability to experimentally induce ICEBs1 in >90% of cells in a population and achieve relatively high conjugation frequencies will allow us to answer previously difficult or unstudied problems fundamental to the ICE lifecycle. We will also identify and analyze host genes needed for ICE function and study interactions between ICEs and other mobile elements in cells. We will extend our analyses to Tn916, a widespread ICE involved in the spread of tetracycline resistance. Our findings should be relevant to the transfer of genes between bacteria growing in many different environments, including the human microbiome. Our work will also focus on several aspects of chromosome dynamics and gene expression. Cells have multiple mechanisms for regulating the initiation of replication. Cells also have regulatory responses to perturbations in replication, often called checkpoints, which control gene expression and cell cycle progression. Coupling gene expression and cell cycle progression to chromosome replication and integrity helps prevent the generation of cells with defective chromosomes. The coordination of genome duplication with cell cycle progression is important for cellular differentiation and preventing uncontrolled cell growth. Microbial pathogenesis often depends on normal bacterial replication and growth in the host. We will use a variety of approaches and methodologies, both in vivo and in vitro, to characterize: the control of replication initiation; regulators of the replication initiator and transcription factor DnaA; and genes controlled in response to perturbations in replication. Understanding these processes in B. subtilis will provide insights regarding similar processes and homologous proteins in a wide variety of organisms, including many Gram positive pathogens.