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

University Of Arizona, Tucson AZ

Investigators

Abstract

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