Our Symbiotic Journey​

Nematodes are among the most abundant and diverse groups of soil fauna, playing essential roles in soil ecology. Among them, entomopathogenic nematodes (EPNs) of the genus Steinernema form remarkable partnerships with naturally occurring mutualistic bacteria of the genus Xenorhabdus. Together, these nematode–bacterium associations have significant potential for agriculture because of their multifaceted antagonistic effects against insect pests. Since their discovery a century ago, EPNs have been widely applied in agriculture, but the lack of stable genetic tools has limited their study. 

At Carnegie Science (2023–26),  the Cao lab has been developing new genetic and synthetic model systems using Steinernema nematodes and Xenorhabdus bacteria to uncover the molecular mechanisms underlying host–microbe signaling. At UW–Madison (starting July 2026), we are expanding this work toward engineering EPN–microbiome interactions in Wisconsin-native species, with the goal of developing innovative and sustainable approaches to agricultural pest management.

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From Soil to Human Health

The value of EPNs extends beyond agriculture. EPN–bacteria pairs serve as an excellent model for studying how animals interact with mutualistic and pathogenic bacteria, including host immune responses, chemical signaling, and behavior. Many of these foundational mechanisms are conserved across animal species, including humans. 

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In addition, EPNs are also powerful models for studying human parasitology. Many human-parasitic nematodes, such as hookworms, share similar life cycles with EPNs but are much harder to maintain and genetically manipulate in the lab. EPNs offer a tractable platform to study host–parasite interactions and develop genetic and engineering tools that could eventually be applied to human parasites. We hope to collaborate with scientists at George Washington University and Caltech to advance EPN-based models for human parasitology.​​