DISSERTATION RESEARCH: Direct Tests of the Adaptive Benefits of Gene Exchange in Evolving Bacterial Populations

个体之间的基因交换是进化变化最重要的因素之一。最近的DNA序列比较表明，细菌种群内经常发生基因交换。本项目以胃细菌幽门螺杆菌为模型系统，研究了基因交换在原核生物中的基础作用。细菌种群内的基因交换能否导致适应速度的提高，以及它能否作为DNA修复的一种手段？为了验证这些假设，将在实验室环境中适应期间测量有和没有遗传交换的幽门螺杆菌种群的适合度。细菌，包括幽门螺杆菌，对人类健康、农业系统和自然环境有重大影响。临床上相关的表型，如抗生素耐药性，可以通过一次基因交换在细菌之间传递。然而，目前尚不清楚这种交换事件是由特定的选择压力揭示的罕见事件，还是一般原核适应机制的结果。了解遗传交换在这些有机体中的基本作用将使人们对这些系统中的种群和进化动态有更广泛的见解。

Genetic exchange between individuals is one of the most important known contributors to evolutionary change.Recent evidence from the comparison of DNA sequences suggests that exchange frequently occurs within bacterial populations.This project utilizes the gastric bacterium Helicobacter pylori as a model system to address two questions concerning the fundamental role of genetic exchange in prokaryotes. Can genetic exchange within bacterial populations lead to increased rates of adaptation and can it function as a means for DNA repair? To test these hypotheses, fitness will be measured in populations of H. pylori, with and without genetic exchange, during adaptation in the laboratory environment. Bacteria, including H. pylori, have a major impact on human health, agricultural systems, and the natural environment. Clinically relevant phenotypes, such as antibiotic resistance, can be passed between bacteria by one instance of genetic exchange. It is not known, however, whether such exchange events represent rare occurrences revealed by specific selective pressures or whether they are the outcomes of a general prokaryotic adaptation mechanism. Understanding the fundamental role of genetic exchange in these organisms will yield broad insights into population and evolutionary dynamics in these systems.