A multi-gene approach to assess phylogenetic relationships of the entomopathogenic bacteria Xenorhabdus spp. (Enterobacteriaceae) and their nematode hosts

昆虫致病细菌Xenorhabdus spp.（肠杆菌科）及其线虫宿主系统发育关系的多基因评估微生物与宿主在不同生物学水平上相互作用。了解微生物如何在宿主之间移动，宿主和微生物如何相互适应，以及微生物-宿主关联的进化后果是至关重要的。昆虫致病菌Xenorhabdus spp.及其线虫（蛔虫）宿主Steinernema spp.代表了陆生动物-微生物共生关系的一种新兴模式。Xenorhabdus spp.在斯坦纳线虫唯一自由生活的阶段被藏在一个特殊的肠道容器中。细菌-线虫对多种昆虫具有致病性，并已成功地在世界范围内实施生物防治计划。PI Stock将研究共生细菌及其线虫宿主的进化历史，考虑多基因库。本文将比较Xenorhabdus和Steinernema的系统发生，以验证这两个伙伴的共同进化和多样化假说。此外，进化模式的生态，生理和形态性状参与这种关联将被检查。这项研究将产生第一个也是最完整的xenorhabdus - steinerma进化亲缘关系假说。此外，它将为记录和解释这种伙伴关系的生态、生理和形态方面提供一个框架。所提出的研究结果也将对共生和微生物生态学领域产生影响。例如，从这项研究中发展出来的系统发育将为理解其他二元共生关系的进化和多样化建立一个框架。

A multi-gene approach to assess phylogenetic relationships of the entomopathogenic bacteria Xenorhabdus spp. (Enterobacteriaceae) and their nematode hostsMicrobes and their hosts interact with each other at different biological levels. Understanding how microbes move between hosts, how host and microbe adapt to each other, and what evolutionary consequences result from microbial-host associations is of fundamental importance. The insect-pathogenic bacteria Xenorhabdus spp. and their nematode (roundworms) hosts, Steinernema spp. represent an emerging model of terrestrial animal-microbe symbiotic relationships. Xenorhabdus spp. are harbored in a specialized intestinal-receptacle in the only free-living-stage of Steinernema nematodes. The bacterium-nematode pair is pathogenic for a wide range of insects and has successfully been implemented in biocontrol programs worldwide. PI Stock will study the evolutionary histories of both symbiotic-bacteria and their nematode-hosts considering a multigene repertoire. Xenorhabdus and Steinernema phylogenies will be compared to test the hypothesis of co-evolution and diversification of these two partners. Additionally, patterns of evolution of ecological, physiological and morphological traits involved in this association will be examined. This research will produce the first and most complete hypothesis of Xenorhabdus-Steinernema evolutionary affinities. Furthermore, it will provide a framework for documenting and interpreting ecological, physiological, and morphological aspects of this partnership. Results from the proposed research will also have implications in the fields of symbioses and microbial ecology. For example, the phylogenies developed from this research will set a framework for understanding the evolution and diversification of other binary mutualistic associations.