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已知的对进化变化最重要的贡献之一。最近来自DNA序列比较的证据表明，交换经常发生在细菌种群中。本项目利用胃幽门螺杆菌作为模型系统来解决关于原核生物遗传交换的基本作用的两个问题。细菌种群内的基因交换是否会导致适应率的提高？它是否可以作为DNA修复的一种手段？为了验证这些假设，将在实验室环境中对幽门螺杆菌种群进行适应性测量，无论是否进行遗传交换。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。临床相关表型，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，尚不清楚这种交换事件是由特定的选择压力所揭示的罕见事件，还是一般的原核生物适应机制的结果。了解遗传交换在这些生物中的基本作用将对这些系统中的种群和进化动力学产生广泛的见解。

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.