Entomopathogenic nematodes (insect-parasitic, EPNs) of the genus Steinernema form remarkable partnerships with mutualistic Xenorhabdus bacteria, creating a powerful binary symbiotic system for addressing foundational questions in host-microbe interactions while offering significant translational potential in agriculture and human health. These partnerships are already widely used for agricultural pest control, yet the lack of stable genetic and synthetic biology tools in EPNs has limited our ability to understand and engineer them. Developing biotechnology for EPNs and their symbiotic bacteria is therefore not only timely but essential to unlocking the full scientific and translational potential of these natural partnerships.
As an Independent Fellow at Carnegie Science (2023–26), Mengyi Cao continued her postdoctoral work to pioneer genetic tools and established the Steinernema–Xenorhabdus partnership as a tractable model for studying binary symbiosis. With these tools, the Cao lab will continue to investigate how animal hosts interact with mutualistic and pathogenic bacteria, with a focus on immunity, chemical signaling, and neurobiology. Now at the University of Wisconsin-Madison, Mengyi is expanding this work to characterize and engineer nematode–microbiome interactions in Wisconsin-native species, with the goal of transforming natural partnerships into new strategies for sustainable agriculture. Beyond agriculture, EPNs also offer tractable models for human parasitology, providing insights and tools that could ultimately advance the study of human-parasitic nematodes.
The Cao lab is headquartered at UW-Madison, where we work closely with colleagues in Entomology and Plant Pathology. Our lab is currently based at Caltech, where we have found an exceptional environment for pioneering genetic and synthetic biology tools for emerging model systems. As Visiting Faculty at Caltech, Mengyi is excited to engage with the Caltech community, collaborate on biotechnology development and beyond, and mentor students and serve on student committees. We look forward to bringing our emerging EPN platform into conversation with Caltech's diverse scientific expertise and, together, exploring how tiny worms can inspire big ideas in biology, biotechnology, sustainable agriculture, and human health.
Publications
Recent Preprints under review and in revision:
†denotes corresponding author; **denotes equal contributions.
Cao, M†. Environmental factors that impact the development of infective juveniles of entomopathogenic nematode Steinernema hermaphroditum. (2026) doi:10.64898/2026.04.07.717109. Under review: Journal of Experimental Biology [link to current preprint].
Xu, M., Ireri, S. W., Prator, M., Lostroh, C. P. & Cao, M†. Establishing a genetic part library for tunable double-stranded RNA circuit construction and RNA interference in Caenorhabditis elegans. (2026) doi:10.64898/2026.03.29.715104. In revision: ACS Synthetic Biology [link to current preprint].
Larsson, E. M., Myers, C. R., Newman, D. K†. & Cao, M†. The nematode symbiotic bacterium Xenorhabdus griffiniae can sense and respond to the presence of its host Steinernema hermaphroditum. (2025) doi:10.1101/2025.06.16.660008. Major revision: Applied and Environmental Microbiology. [link to current preprint]
Progress report: Ireri, S. W. and Cao, M†. CRISPR-Cas9 gene editing in the agriculturally beneficial entomopathogenic nematode Steinernema feltiae. BioRxiv 2025.07.18.665633 (2025) doi:10.1101/2025.07.18.665633. [link to current preprint]
Cao, M†. CRISPR-Cas9 genome editing in Steinernema entomopathogenic nematodes. bioRxiv 2023.11.24.568619 (2023) doi:10.1101/2023.11.24.568619. Minor revision with no further experiments in Genetics. [link to current preprint]
Peer-reviewed publications:
Chen, V., Marken, J. P., Murray, R. M. & Cao, M†. Escherichia coli Nissle 1917 Occupies Previously Undocumented Host Niches in the Insect‐Parasitic Nematode Steinernema hermaphroditum. Environ. Microbiol. Rep. 18, (2026). [link to paper]
Ireri, S. W. & Cao, M†. CRISPR-Cas9-based Mutagenesis in the Entomopathogenic Nematode Steinernema hermaphroditum and the Maintenance of Mutant Lines. J. Vis. Exp: JoVE (2025) doi:10.3791/68932. [link to paper]
Heppert, J. K. Awori, RM. Cao, M. Chen, G. Mcleish, J. Goodrich-Blair, H. Analyses of Xenorhabdus griffiniae genomes reveal two distinct sub-species that display intra-species variation due to prophages. BMC Genom. 25, 1087 (2024). [link to paper]