Biophysical Society Thematic Meeting | Ascona 2026

Mechanobiology of Infection

Poster Abstracts

12-POS Board 12 ADAPTATION OF CLOSTRIDIOIDES DIFFICILE TO COLON-RELEVANT MECHANICAL STRESS Po-Long Hsiao 1,2 ; Alexandre Persat 1,2 ; Clostridioides difficile is a clinically significant opportunistic pathogen that targets the colon, where it drives lethal tissue injury and frequently recurs following initial infection. To establish colonization, C. difficile must transition from a planktonic lifestyle to a sessile state. This process requires the bacterium to detect host surfaces and respond through coordinated transcriptional and metabolic changes that support survival and growth in this niche, yet the physiological mechanisms underlying surface colonization remain poorly understood. Here, we reveal the transcriptomic signature of the C. difficile strain 630 Δ erm during adaptation to an abiotic surface. We found that the ability of utilizing a substantial carbon source in the colon, ethanolamine, was strongly enhanced during adaptation to the surface. Meanwhile, multiple osmo-related genes were drastically modulated on the surface, indicating that C. difficile experienced hyperosmotic conditions that imitate host colonic lumen. To monitor the dynamics of the transcriptional activation of the ethanolamine utilization genes (eut operon) at single-cell resolution, we engineered transcriptional fluorescent reporter for anaerobic live-cell imaging. We show that the transcriptional reporter for eutS is activated upon surface association and under hyperosmotic liquid conditions, suggesting those mechanical signals stimulate ethanolamine utilization. Consistent with this, we show that surface growth pre-conditions C. difficile to utilize ethanolamine. Finally, we tested the infection models leveraging tissue engineered human colonic organoid for high-resolution visualization of C. difficile behavior at mucosa. Our results indicate that C. difficile metabolically adapts to the mucosal environment upon mechanical stimulation, potentially promoting its persistence. 1 Global Health Institute, EPFL, Lausanne, Switzerland 2 Institute of Bioengineering, EPFL, Lausanne, Switzerland

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