Mengyi

Cao

The Cao lab investigates microbial symbiosis between the insect-parasitic nematodes in the genus of Steinernema and their mutualistic bacterial partners from the genus Xenorhabdus. In addition to their ecological importance in soil ecosystems and practical value in promoting sustainable agriculture, these symbiotic pairs are valuable models for studying how animals and microbes adapt to changing environments. The Cao group is focused on establishing Steinernema hermaphroditum as a genetic model, with particular emphasis on its interactions with the mutualistic symbiotic bacterium Xenorhabdus griffiniae and the mild pathogen E. coli Nissle. Our current research investigates how X. griffiniae and E. coli Nissle colonize distinct intestinal tissues in S. hermaphroditum and elicit unique host responses at the transcriptional, biochemical, and behavioral levels.

To further investigate the immunological and neurological responses of Steinernema nematodes to both symbionts and pathogens, a major hurdle has been the lack of molecular genetic tools—particularly on the host side. To address this, our group began developing such tools, including CRISPR-Cas9–based genome editing in Steinernema. On the symbiotic bacterial side, we are building a synthetic biology toolkit by establishing a modular library in Xenorhabdus, which enables microbial engineering with broad applications, including the potential of RNAi delivery to the host. Together, these toolkits will accelerate our efforts to answer fundamental questions in microbial symbiosis and translate our findings into innovative strategies for environmental engineering—for example, designing bacterial biosensors capable of detecting nematodes in the soil ecosystem. 

†denotes corresponding author publications. **denotes equal contribution as co-first authors.

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. (2025) doi:10.1101/2025.07.03.663106. Submitted to Environmental Microbiology. [link to current preprint]

Larsson, E. M., Myers, C. R., Newman, D. K†. & Cao, M†. The nematode symbiotic bacterium Xenorhabdus griffiniaecan sense and respond to the presence of its host Steinernema hermaphroditum. (2025) doi:10.1101/2025.06.16.660008. Under review: Applied and Environmental Microbiology. [link to current preprint]

Heppert, J. K. Awori, RM. Cao, M. Chen, G. Mcleish, J. Goodrich-Blair, H. Analyses of Xenorhabdus griffiniaegenomes reveal two distinct sub-species that display intra-species variation due to prophages. BMC Genom. 25, 1087 (2024). [link to paper]

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 in Genetics.[link to current preprint]

Cao, M†., Schwartz, HT, Tan, C-H and Sternberg, PW†. The entomopathogenic nematode Steinernema hermaphroditum is a self-fertilizing hermaphrodite and a genetically tractable system for the study of parasitic and mutualistic symbiosis. Genetics 220, (2022). [link to paper]

Mucci NC, Jones KA, Cao M, Wyatt MR 2nd, Foye S, Kauffman SJ, Richards GR, Taufer M, Chikaraishi Y, Steffan SA, Campagna SR, and Goodrich-Blair H. Apex predator nematodes and meso-predator bacteria consume their basal insect prey through discrete stages of chemical transformations. mSystems. 7(3), e0031222 (2022). [link to paper]

Cao, M and Goodrich‐Blair, H. Xenorhabdus nematophila bacteria shift from mutualistic to virulent Lrp‐dependent phenotypes within the receptacles of Steinernema carpocapsae insect‐infective stage nematodes. Environ Microbiol22, 5433–5449 (2020). [link to paper]

Stilwell, MD**, Cao, M**, Goodrich-Blair, H and Weibel, DB. Studying the symbiotic bacterium Xenorhabdus nematophila in individual, living Steinernema carpocapsae nematodes using microfluidic systems. mSphere 3, e00530-17 (2018). [link to paper]

Cao, M, Patel, T, Rickman, T, Goodrich-Blair, H, and Hussa, EA. High levels of the Xenorhabdus nematophilatranscription factor Lrp promote mutualism with the Steinernema carpocapsae nematode host. Appl Environ Microb83, e00276-17 (2017). [link to paper]

Cao, M†, and Goodrich-Blair, H. Ready or not: Microbial adaptive responses in dynamic symbiosis environments. J Bacteriol 199, e00883-16 (2017). [link to paper]