COBRE: UID: PROJ 2: EVOLUTION OF ANTIBIOTIC RESISTANCE PLASMIDS

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。质粒是可移动的遗传元素，在细菌物种之间抗生素耐药性的分散中发挥核心作用，从而降低用于治疗传染病的抗菌剂的有效性。我们的研究目的是通过实验进化研究来辨别质粒进化的模式。特别是，我们的目标是确定一些质粒如何进化出在广泛的宿主中转移和维持的能力。64.5 kb的IncP-1？选择质粒pB10作为模型系统是因为它具有高可转移性和广泛的宿主范围。对该质粒在污水处理厂细菌群落中的天然宿主范围的研究表明，pB10转移到38个不同的物种。这些发现还表明，质粒的宿主范围不仅取决于质粒本身的特性，还取决于原始宿主和环境参数。从这些研究中，我们发现两个宿主的质粒pB10比大肠杆菌K12表现出更高的负担或更不稳定。在其中一种宿主，p.p putida H2 （pB10）的进化实验中，质粒对以前从未携带过质粒的等基因H2菌株（na¿ve）的成本在1000代质粒进化后显著降低：从20%降至9%或16%，具体取决于质粒是否在等基因宿主之间定期转移。这些结果表明，质粒编码的适应性变化是这种剧烈的质粒宿主适应的原因，分子基础正在研究中。同时，将三个天然存在的IncP-1质粒的基因组序列与已知的IncP-1质粒的基因组序列进行比较。对照两个所有其它测序的IncP-1？质粒pB3的oriV区不被转座子打断，这为这些混杂质粒的进化史提供了新的线索。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Plasmids are mobile genetic elements that play a central role in the dispersion of antibiotic resistance among bacterial species, thereby decreasing the effectiveness of antimicrobial agents used for the treatment of infectious diseases. The objective of our research is to discern patterns of plasmid evolution through experimental evolution studies. In particular, we aim to determine how some plasmids have evolved the ability to transfer and be maintained in a wide range of hosts. The 64.5 kb IncP-1? plasmid pB10 was chosen as a model system because of its high transferability and broad host-range. An examination of the natural host-range of this plasmid in the bacterial community of a sewage treatment plant showed that pB10 transferred to 38 distinct species. These findings also suggested that the host-range of a plasmid was not only determined by intrinsic plasmid characteristics but by the original host and the environmental parameters. From these studies we found two hosts in which plasmid pB10 presents a higher burden or is less stable than in E. coli K12. In an evolution experiment with one of these hosts, P. putida H2 (pB10), the cost of the plasmid to an isogenic H2 strain that had never carried the plasmid before (na¿ve), was significantly decreased after 1000 generations of plasmid evolution: from 20% to 9% or 16%, depending on whether or not the plasmid was regularly transferred between isogenic hosts. These results indicate that plasmid-encoded adaptive changes were responsible for this drastic plasmid-host adaptation, and the molecular basis is being examined. In parallel, the genome sequences of three naturally occurring IncP-1 plasmids were compared with those of known IncP-1 plasmids. In contrast two all other sequenced IncP-1? plasmids, the oriV region of plasmid pB3 is not interrupted by transposons, shedding new light on the evolutionary history of these promiscuous plasmids.