Conjugal Transfer of Bacteroides Antibiotic Resistances

描述(申请人提供)：抗生素耐药性发生率为 在许多组致病细菌中都在增加。虽然有些细菌 通过突变获得抗生素而对抗生素产生抗药性 来自其他细菌的抗药性基因可能更常见。这项建议 主要研究类杆菌属。类杆菌属在数量上属于 人类结肠中的主要细菌种类。类杆菌属物种有 也是可能导致危及生命的感染的机会性病原体。许多 类杆菌菌株已经对多种抗生素产生了抗药性。转让 这些菌株之间的抗药性基因似乎主要通过 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， 它通过接合方式传输到接收方，并集成到 接受者的染色体。在之前的资助期间，负责 对于切除和转移被识别并被证明由一个 一组复杂的调控基因。这些基因可能允许CTN协调 切除并转移，以便划痕以启动圆形形式的转移 在切除完成之前不会发生。切除和转移都是 被抗生素四环素刺激1000倍以上。此前，我们发现 这三个基因rteA、rteB和rteC是中枢调控基因。我们 提出RTEC可触发两个切除基因exA和exB的表达。这个 该提案的第一个具体目标是检验这一假设。第二个目标 是为了确定ExcA和ExcB如何与CTN整合酶协同工作 (Int)，催化CTN的切割和环化。第三个具体目标 就是确定RTEC目前是否也控制着基因的表达 指定为orf5，并测试Orf5反过来控制 转移(Tra)基因的表达。第四个具体目标是回答 切除和转移的协调到底有多有效的问题。 最后一个目的是确定RteA和RteB的特征和功能， 它们控制着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.