Our research is aimed at understanding how microbes survive and flourish in the environments they occupy. Survival for many microbes is dependent upon their ability to interact with other organisms. To understand host-microbe interactions, our lab focuses on a gamma-proteobacterium, Xenorhabdus nematophila. This bacterium is a symbiont of the insect-infecting nematode Steinernema carpocapsae.

X. nematophila resides within a specialized intestinal vesicle of the nematode. Each of these two organisms requires the other to grow and reproduce, a process that occurs within the insect. The bacterium, X. nematophila, is the actual insect pathogen; it produces exo- and endo-toxins that can rapidly kill an insect host. In addition, once inside an insect host, X. nematophila expresses degradative functions such as proteases and lipases that convert insect host tissues into products that can be utilized by the nematode. Thus, X. nematophila is essential for both insect host killing and nematode development.

Furthermore, X. nematophila is part of a tripartite system (insect, nematode, and bacterium) that has potential use as an alternative to insecticides. Understanding the relationship between the members of this system will greatly improve their use in biocontrol. In our work we use molecular, genetic, and biochemical techniques to ask basic biological questions involving the interaction of X. nematophila with its hosts, examining the interaction from both the bacterium and host sides.

• Microbiology 470: Microbial Genetics & Molecular Machines

• Microbial Symbiosis at UW-Madison
• Co-Director, Microbes in Health and Diseases Training Program
• Microbial Pathogenesis and Host Responses Group
• Co-Director, Nematode-Bacterium Symbioses Research Coordination Network