Cell-Cell Signaling, Gene Expression, and Horizontal Gene Transfer in Bacillus

描述(申请人提供)：水平基因转移(HGT)是细菌进化的驱动力，使细菌能够获得新的基因和表型。水平基因转移在很大程度上是由可移动的遗传元件介导的，包括病毒、接合质粒和整合和接合元件(ICs)，也称为接合转座子。结合元件是众所周知的促进抗生素耐药性、发病机制、共生、新陈代谢等基因传播的因素，并在很大程度上导致耐药和多药耐药细菌病原体的激增。冰在细菌中广泛存在，似乎是最普遍的结合元件类型。它们存在于宿主基因组中。在某些条件下，它们可以切除形成一个圈，然后单链DNA可以被转移到合适的受体细胞。除了调节自身的转移外，ICE还可以动员(转移)其他DNA元件，包括不能自我转移的质粒。尽管ICE的流行和重要性，但我们对这些可移动的遗传因素的理解存在根本性的缺陷。ICE功能的许多基本机制尚不清楚，尤其是在革兰氏阳性菌中。细菌宿主成分在ICE生物学中起着关键作用，但这些宿主成分在ICE生命周期中的身份和功能在很大程度上是未知的。冰通常与其他可移动的遗传元素共存，包括噬菌体。尽管这些元素同时出现，但人们对这些元素对彼此的影响知之甚少。可移动遗传元件ICEBs1是枯草芽孢杆菌中的一个整合和结合元件。ICEBs1基因的表达、切除和交配是在DNA损伤(SOS反应)后和拥挤的条件下诱导的，前提是邻近细胞不包含该元件的副本。在实验中在一个群体中几乎所有细胞中诱导ICEBs1的能力 达到相对较高的共轭频率允许我们回答以前难以解决的或未被研究的问题，这些问题是共轭和HGT的基础。该项目将集中在：1)新发现的ICEBs1似乎具有广泛保守性的特性，2)鉴定和阐明对ICEBs1生活史至关重要的宿主功能，以及3)表征ICEBs1与许多枯草杆菌基因组中发现的溶原噬菌体之间的相互作用。基于冰的同源性和保守的生命周期，从研究ICEBs1及其宿主枯草杆菌获得的见解很可能普遍适用于许多其他移动电话 遗传因素和它们的宿主。我们的发现应该与生长在许多不同环境中的细菌之间的基因转移有关，包括那些编码抗生素耐药性的基因，包括人类。

DESCRIPTION (provided by applicant): Horizontal gene transfer (HGT) is a driving force in bacterial evolution, permitting bacteria to acquire new genes and phenotypes. Horizontal gene transfer 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, and are largely responsible for the surge in drug- resistant and multi-drug-resistant bacterial pathogens. ICEs are widespread in bacteria and appear to be the most prevalent type of conjugative element. They reside integrated in a host genome. Under certain conditions, they can excise to form a circle and then a single strand of DNA can be transferred to appropriate recipient cells. In addition to mediating their own transfer, ICEs can mobilize (transfer) other DNA elements, including plasmids, that are not able to self-transfer. Despite the prevalence and importance of ICEs, there are fundamental deficiencies in our understanding of these mobile genetic elements. Many basic mechanisms of ICE function are not well understood, especially in Gram-positive bacteria. Components of the bacterial host components play key roles in ICE biology, but the identities and functions of these host components in the ICE life-cycle are largely unknown. ICEs commonly co-exist with other mobile genetic elements, including phages. Despite this co-occurrence, little is known about effects these elements have on one another. The mobile genetic element ICEBs1 is an integrative and conjugative element in Bacillus subtilis. ICEBs1 gene expression, excision, and mating are induced following DNA damage (the SOS response) and under conditions of crowding, provided that the neighboring cells do not contain a copy of the element. The ability to experimentally induce ICEBs1 in virtually all cells in a population and achieve relatively high frequencies of conjugation allow us to answer previously intractable or unstudied problems fundamental to conjugation and HGT. This project will focus on: 1) newly discovered properties of ICEBs1 that appear to be broadly conserved, 2) identifying and elucidating host functions that are important for ICEBs1 life cycle, and 3) characterizing interactions between ICEBs1 and a lysogenic phage found in the genome of many strains of B. subtilis. Based on homologies and the conserved life cycle of ICEs, insights gained from studying ICEBs1 and its host, B. subtilis, are likely to be generally relevant to many other mobile genetic elements and their hosts. Our findings should be relevant to the transfer of genes, including those encoding antibiotic resistances, between bacteria growing in many different environments, including humans.