Conjugal Transfer of Bacteroides Antibiotic Resistances

描述（由申请人提供）：抗生素耐药性的发生率为 在许多致病菌群中不断增加。虽然有些细菌 通过突变，获得抗生素， 来自其他细菌的耐药基因可能更常见。这项建议 主要研究拟杆菌属。拟杆菌属物种在数量上属于 人类结肠中的主要细菌种类。拟杆菌属物种是 也包括可能导致危及生命的感染的机会性病原体。许多 拟杆菌菌株已对多种抗生素产生耐药性。转让 这些菌株中的抗性基因似乎主要通过以下途径产生： 一组共轭转座子（CTn）的作用，由 CTnDOT。CTnDOT从染色体上切除形成环状中间体， 其通过缀合转移到受体并整合到 接受者的染色体。在上一个资助期间，基因负责 的切除和转移，并表明是由一个 复杂的调控基因。这些基因可以使CTn协调 切除和转移，以便切口开始转移圆形 直到切除完成才发生。切除和转移都是 抗生素四环素的刺激超过一千倍之前我们发现 rteA、rteB和rteC三个基因作为中枢调控基因发挥作用。我们 提出RteC触发两个切除基因excA和excB的表达。的 该提案的第一个具体目标是检验这一假设。第二个目的 是为了确定ExcA和ExcB，可能与CTn整合酶一起， (Int)催化CTn的切除和环化。第三个具体目标 是确定RteC是否也控制着目前 命名为orf5，并测试假设orf5反过来控制 转移（TRA）基因的表达。第四个具体目标是回答 切割和转移之间的协调实际上如何有效的问题。 最后一个目的是明确RteA和RteB的特征和功能， 其控制rteC的表达。

DESCRIPTION (provided by applicant): The incidence of antibiotic resistance is increasing in many groups of disease-causing bacteria. Although some bacteria become resistant to antibiotics through mutation, acquisition of antibiotic resistance genes from other bacteria is probably more common. This proposal focuses on the genus Bacteroides. Bacteroides species are among the numerically predominant species of bacteria in the human colon. Bacteroides species are also opportunistic pathogens that can cause life-threatening infections. Many Bacteroides strains have become resistant to multiple antibiotics. Transfer of resistance genes among these strains appears to have occurred mainly through the actions of a group of conjugative transposons (CTns), represented by CTnDOT. CTnDOT excises from the chromosome to form a circular intermediate, which transfers by conjugation to a recipient and integrates into the recipient's chromosome. During the previous funding period, genes responsible for excision and transfer were identified and shown to be controlled by a complex set of regulatory genes. These genes may allow the CTn to coordinate excision and transfer so that nicking to initiate transfer of the circular form does not occur until excision is complete. Both excision and transfer are stimulated over 1,000-fold by the antibiotic tetracycline. Previously, we found that three genes, rteA, rteB and rteC function as central regulatory genes. We propose that RteC triggers expression of two excision genes, excA and excB. The first specific aim of the proposal is to test this hypothesis. The second aim is to determine how ExcA and ExcB, presumably in concert with the CTn integrase (Int), catalyze excision and circularization of the CTn. The third specific aim is to determine whether RteC also controls expression of a gene currently designated as orf5 and to test the hypothesis that Orf5 in turn controls the expression of transfer (tra) genes. The fourth specific aim is to answer the question of how effective coordination of excision and transfer actually is. The last aim is to define the characteristics and functions of RteA and RteB, which control expression of rteC.